铜厚膜环行器的研制

采用新型的在大气气氛中烧结的铜厚膜多层导电浆料,应用厚膜混合技术制作了2。2GHz和2.8GHz的环行器。其性能指标可与同类型采用薄膜贵金属制作的环行器相媲美,且工艺简单,成本低及生产周期短。     

基于AlGaN/GaN HEMT的C波段混合集成功率合成放大器的设计

研制了一种基于AlGaN/GaN HEMT的功率合成技术的混合集成放大器电路.该电路包含4个10×120 μm的HEMT晶体管以及一个Wilkinson功率合成器和分配器.在偏置条件为VDS=40V,IDS=0.9A时,输出连续波饱和功率在5.4GHz达到41.4dBm,最大的PAE为32.54%,并且功率合成效率达到69%.     

开关型电压调节器MIC4680及其应用电路

MIC4680是Micrel公司推出的一种新型开关型电压调节器。它在4－34V的输入电压范围内能输出稳定的固定或要调输出电压。可广泛应用于电源调节卡、正负电压转换器、电池充电以及能驱动外部FET的高电路输出调节系统中。文中介绍了它的主要特点、引脚功能、主要参数和可调输出时的典型电路及设计方法。最后给出了由MIC4680构成的手机电池充电电路和将正＋12V转换成－12V输出的正、负电压转换器等实际电路。     

壳多糖抑制细菌生长的构效关系

运用化学结构已清楚, 分属4大系列的29种壳多糖, 以4种不同类型的细菌(革兰氏阳性菌Ecoli K1、革兰氏阴性菌Bacillus cereus、Bacillus megaterium和Staphlylococcu aureus)为研究对象, 进行了壳多糖抑菌能力构效关系的研究. 在实验中采用96孔平板, 用计算机\|吸光值读数仪直接测定每个孔的吸光值, 获得了各个细菌在不同壳多糖浓度中的生长曲线和壳多糖抑制细菌生长的最低抑制浓度(MIC, Minimum inhibit concentration). 通过比较同一(各个)系列的壳多糖在这些相同(不同)细菌的MIC变化规律与壳多糖的化学结构的关系, 发现同一壳多糖对不同的细菌的MIC值是不相同的, 因而壳多糖抑制细菌生长的能力首先与细菌本身特点有关, 但与是否为革兰氏阳性菌或阴性菌无直接的相关性; 同一细菌对不同化学结构的壳多糖有一定的相关性, 在壳多糖的聚合程度(DP)相同的条件下, 壳多糖中氨基被乙酰化(DA)的程度越低, 壳多糖抑制细菌生长的MIC值越低, 壳多糖抑制细菌生长的能力就越强; 同样,在DA相同的情况下, 分子越小, 壳多糖抑制细菌生长的MIC值越低, 抑制细菌生长的能力越强. 根据上述实验结果, 初步推测壳多糖抑制细菌生长的机制可能与其在溶液中所带的正电荷多少有关.     

Synthesis and antimicrobial screening of 1,3,4-oxadiazole and clubbed thiophene derivatives

In the present study, a novel series of 2-{5-[4-(1-aza-2-(2-thienyl)vinyl)phenyl](1,3,4-oxadiazol-2-ylthio)}-N-arylacetamides (IV)_1–12 were synthesized and tested for their antimicrobial activity. Newly synthesized compounds were screened for their antibacterial and antifungal activities on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus pyogenes, Candida albicans, Aspergillus niger and Aspergillus clavatus. The chemical structures of newly synthesized compounds were elicited by IR, ¹H NMR, ¹³C NMR and mass spectral data. The synthesized bio-active compounds exhibited excellent to moderate antimicrobial activity. Compounds (IV)₅, (IV)₆ and (IV)₇ possess excellent antibacterial activity whereas compounds (IV)₆, (IV)₉ and (IV)₁₁ possess excellent antifungal activity.     

Design,synthesis and antimicrobial evaluation of thioglycosides of a novel class of 2-mercaptonicotinonitriles

A new class of thioglycosides comprising a diazenyl pyridine moiety was assembled from the regioselective reaction of the acetylated α-glycopyranosyl bromide with hitherto unreported 2-mercaptonicotinonitriles. Moreover, the deacetylation of S-glycoside derivatives utilizing of methanolic ammonia solution afforded the free hydroxy thioglycosides in quantitative yields. The identity of the newly obtained derivatives has been achieved via spectroscopic and elemental analyses. All of the newly synthesized derivatives exhibited significant antimicrobial activity towards certain selected microorganisms (bacteria and fungi). Generally, S-glycoside derivatives demonstrated outstanding antibacterial and antifungal activities. Amongst them, the acetylated derivatives showed the most distinguished antifungal and antibacterial activities with a promising minimum inhibitory concentration (MIC) values in comparison with the approved drugs; Amphotericin B and Cefotaxime.     

Synthesis and antimicrobial characterization of novel l-lysine gemini surfactants pended with reactive groups

A series of novel quaternary ammonium gemini surfactants of l-lysine containing ester group were synthesized with high yield rate. The antibacterial and antifungal activities of these gemini surfactants were evaluated by quantifying the minimal inhibitory concentration (MIC). The results indicated that the quaternary ammonium gemini surfactants exhibited improved activity against a broad spectrum of Gram-positive and Gram-negative bacteria as well as fungi. The pended ester group provides a reactive site for incorporating the surfactant into polymers, thus leading to the polymers with high antimicrobial efficiency.     

Potential Efficacy of β-Amyrin Targeting Mycobacterial Universal Stress Protein by In Vitro and In Silico Approach

The emergence of drug resistance and the limited number of approved antitubercular drugs prompted identification and development of new antitubercular compounds to cure Tuberculosis (TB). In this work, an attempt was made to identify potential natural compounds that target mycobacterial proteins. Three plant extracts (A. aspera, C. gigantea and C. procera) were investigated. The ethyl acetate fraction of the aerial part of A. aspera and the flower ash of C. gigantea were found to be effective against M. tuberculosis H₃₇Rv. Furthermore, the GC-MS analysis of the plant fractions confirmed the presence of active compounds in the extracts. The Mycobacterium target proteins, i.e., available PDB dataset proteins and proteins classified in virulence, detoxification, and adaptation, were investigated. A total of ten target proteins were shortlisted for further study, identified as follows: BpoC, RipA, MazF4, RipD, TB15.3, VapC15, VapC20, VapC21, TB31.7, and MazF9. Molecular docking studies showed that β-amyrin interacted with most of these proteins and its highest binding affinity was observed with Mycobacterium Rv1636 (TB15.3) protein. The stability of the protein-ligand complex was assessed by molecular dynamic simulation, which confirmed that β-amyrin most firmly interacted with Rv1636 protein. Rv1636 is a universal stress protein, which regulates Mycobacterium growth in different stress conditions and, thus, targeting Rv1636 makes M. tuberculosis vulnerable to host-derived stress conditions.     

Solvent-Free Synthesis,In Vitro and In Silico Studies of Novel Potential 1,3,4-Thiadiazole-Based Molecules against Microbial Pathogens

A new series of 1,3,4-thiadiazoles was synthesized by the reaction of methyl 2-(4-hydroxy-3-methoxybenzylidene) hydrazine-1-carbodithioate (2) with selected derivatives of hydrazonoyl halide by grinding method at room temperature. The chemical structures of the newly synthesized derivatives were resolved from correct spectral and microanalytical data. Moreover, all synthesized compounds were screened for their antimicrobial activities using Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, Bacillus subtilis, Staphylococcus aureus, and Candida albicans. However, compounds 3 and 5 showed significant antimicrobial activity against all tested microorganisms. The other prepared compounds exhibited either only antimicrobial activity against Gram-positive bacteria like compounds 4 and 6, or only antifungal activity like compound 7. A molecular docking study of the compounds was performed against two important microbial enzymes: tyrosyl-tRNA synthetase (TyrRS) and N-myristoyl transferase (Nmt). The tested compounds showed variety in binding poses and interactions. However, compound 3 showed the best interactions in terms of number of hydrogen bonds, and the lowest affinity binding energy (−8.4 and −9.1 kcal/mol, respectively). From the in vitro and in silico studies, compound 3 is a good candidate for the next steps of the drug development process as an antimicrobial drug.     

Synthesis,and characterization of some Cu(I) complexes having propionitrile and pyridine moieties: An investigation on their antibacterial properties

The aim of producing new biologically active compounds lead to the synthesis of some Cu(I) complexes of general formula [Cu(C₂H₅CN)₄][A] and [Cu(C₅H₅N)₄][A] (1–4) {where A: counter anion = B(C₆F₅)₄⁻ and B{C₆H₃(m-CF₃)₂}₄⁻} from the reaction of CuCl and silver salt of the corresponding counter anion. The complexes were characterized using elemental analysis, ¹H NMR, ¹¹B NMR, FT-IR Spectroscopy, UV–visible spectroscopy and thermo-gravimetric analysis (TGA). The antibacterial activities of all complexes are evaluated by the minimal inhibitory concentration (MIC), using the micro-broth dilution method, against eight bacteria (Gram-negative and Gram-positive), each with fresh clinical isolates. The MIC results were compared with those of Oxytetracycline agent as a positive control. In most cases, the compounds show broad-spectrum activities that were either, more active, or equipotent to, the antibiotic agent in the comparison tests. Complex 4 showed the greatest activity against Proteus mirabilis (Gram- negative) with a minimum inhibitory concentration (MIC) of 8 µg/mL, while complexes 2 and 3 showed the lowest activity against Pseudomonas aeruginosa (Gram-negative) and against Staphylococcus aureus (Gram-positive) with a concentration of 512 µg/mL.