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121.
Considering a two DoF system subject to digital position control, of interest for robotic application, we analyze the dynamics of the system at the intersection of two loci of Neimark–Sacker bifurcations, where a double Neimark–Sacker bifurcation is taking place. In the system, the saturation of the control force is the only nonlinear term considered, other than this, the system is piecewise linear. Starting from the analytical investigation already performed in Part I (Habib et al. in Nonlin. Dyn., under review, 2013), in this paper the effects of an asymmetry of the saturation of the control force are investigated, both analytically and numerically. The results show the increasing complexity of the dynamics for a more and more asymmetric system. First, the asymmetry is making the bifurcation transit from supercritical to subcritical, then it generates a stable torus that breaks down into a strange attractor, associated with a chaotic motion. In the last part of the paper, the torus breakdown and the onset of chaos are investigated, furthermore the evolution of complex dynamics through regions of phase locking and higher-dimensional chaos is outlined. 相似文献
122.
Uzma Habib Amin Badshah Ulrich Flörke Rizwana Aleem Qureshi Bushra Mirza Nazar-ul-Islam Azeem Khan 《Journal of chemical crystallography》2009,39(10):730-734
Abstract The reaction of Cu(OOCCH3)2·H2O with (2,4-diamino-5-(3′,4′,5′-trimethoxybenzyl) pyrimidine (trimethoprim) in ethanolic solution at 80 °C affords the title
complex which has been characterized by elemental, IR, and NMR (1H and 13C).The crystal structure has been determined by single crystal X-ray diffraction. Compound 1 (C36H48Cu2N8O14) is triclinic, space group P-1 with a = 7.2676(4) ?, b = 11.6721(7) ?, c = 12.8279(8) ?, α = 95.839(1)°, β = 93.456(1)°, γ = 105.541(1)°, Z = 1. Two copper atoms are coordinated directly to each other as well as are held together by four bridging aceto groups.
Each copper atom is also bonded opposite the Cu–Cu vector to a trimethoprim molecule through the N(1) atom of the pyrimidine
ring. Trimethoprim acts as a monodentate ligand through the pyrimidine nitrogen N(1) atom. The complex was screened for the
activity against several bacteria, showing more activity against bacteria as compared to trimethoprim.
Graphical Abstract To enhance the activity of trimethoprim, its derivative was prepared and there bacterial activity against several bacteria
was analyzed.
相似文献
123.
Uzma Habib Amin Badshah Ulrich Flörke Rizwana Aleem Qureshi Bushra Mirza Nazar-ul-Islam Azeem Khan 《Journal of chemical crystallography》2009,39(8):607-611
Abstract The title copper (II) complex with Trimethoprim was prepared at 20–25 °C and its crystal structure was determined by single
crystal X-ray diffraction. Compound (C36H50Cu3N8O16) is triclinic, space group P-1 with a = 6.4642(5) ?, b = 12.5495(9) ?, c = 13.4911(10) ?, α = 77.518(1)°, β = 85.326(1)°, γ = 84.413(2)°, Z = 1. In this compound, three copper atoms are bonded to each other, two terminal coppers are bonded to three oxygen atoms
and N1 of pyrimidine ring of Trimethoprim and central copper is bonded to four oxygen atoms. The amino nitrogen atoms are not involved
in the coordination to the metal.
Graphical Abstract To enhance the activity of trimethoprim, its derivative was prepared and there bacterial activity against several bacteria
was analyzed.
相似文献
124.
M. Selim Habib M. Mejbaul Haque M. Samiul Habib M.I. Hasan M. Shaifur Rahman S.M.A. Razzak 《Optik》2014
We report on a highly birefringent holey fiber for broadband dispersion compensation covering the S, C, and L telecommunication bands i.e. wavelength ranging from 1460 to 1625 nm. The finite element method with circular perfectly matched layer boundary condition is used to investigate the guiding properties. Numerical analysis demonstrates that it is possible to obtain negative dispersion coefficient of about −470 to −850 ps/nm/km over S to L-bands and a relative dispersion slope perfectly matched with single mode fiber (SMF) of about 0.0036 nm−1 at 1550 nm. At the same time birefringence of the order 2.53 × 10−2 is realized at 1550 nm wavelength. Owing to superior optical properties of the proposed holey fiber, this can be a promising candidate for broadband dispersion compensation and sensing applications. 相似文献
125.
In this paper, we present a photonic crystal fiber based on hexagonal structure for improved negative dispersion as well as high birefringence in the telecom wavelength bands. It is demonstrated that it is possible to obtain negative dispersion coefficient of −712 ps/(nm km) and relative dispersion slope (RDS) perfectly match to that of single mode fiber (SMF) of about 0.0036 nm−1 at the operating wavelength 1550 nm. The proposed fiber exhibits high birefringence of the order 2.11 × 10−2 with nonlinear coefficient about 57.57 W−1 km−1 at 1550 nm. Moreover, it is confirmed that the designed fiber successfully operates as a single mode in the entire band of interest. 相似文献
126.
Zubida Habib M. Ikram Kowsar Majid K. Asokan 《Applied Physics A: Materials Science & Processing》2014,116(3):1327-1335
A series of samples of HoFe1?x Ni x O3 (x = 0.0, 0.1, 0.3) were prepared using the solid-state reaction technique to understand the structural, dielectric and conductivity properties before and after gamma irradiation of accumulated dose of 625 KGy. The X-ray diffraction confirms that all the samples exist in single-phase orthorhombic structure having space group Pbnm. With increasing dopant Ni, the unit cell volume and lattice parameters undergo small change. X-ray analysis show change in the interplanar spacing and full width at half maximum values after gamma irradiation. The Raman spectra of the samples show modifications after gamma irradiation. It can be easily seen that after gamma irradiation intensity, peak width are completely altered by gamma-absorbed dose. Measurement of dielectric loss and dielectric constant at room temperature was performed before and after gamma irradiation in the frequency range of 20 Hz–1 MHz. It is observed that the value of dielectric constant decreases after irradiation. The ac conductivity is estimated from the dielectric constant and loss tangent. Exposure to gamma radiation results in substantial modification in the physical properties of the Ni-doped Ho-based orthoferrites. 相似文献
127.
Malgorzata Frik Dr. Josefina Jiménez Ismael Gracia Prof. Larry R. Falvello Sarya Abi‐Habib Karina Suriel Prof. Theodore R. Muth Prof. María Contel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(12):3659-3674
The reaction of new dinuclear gold(I) organometallic complexes containing mesityl ligands and bridging bidentate phosphanes [Au2(mes)2(μ‐LL)] (LL=dppe: 1,2‐bis(diphenylphosphano)ethane 1 a , and water‐soluble dppy: 1,2‐bis(di‐3‐pyridylphosphano)ethane 1 b ) with Ag+ and Cu+ lead to the formation of a family of heterometallic clusters with mesityl bridging ligands of the general formula [Au2M(μ‐mes)2(μ‐LL)][A] (M=Ag, A=ClO4?, LL=dppe 2 a , dppy 2 b ; M=Ag, A=SO3CF3?, LL=dppe 3 a , dppy 3 b ; M=Cu, A=PF6?, LL=dppe 4 a , dppy 4 b ). The new compounds were characterized by different spectroscopic techniques and mass spectrometry The crystal structures of [Au2(mes)2(μ‐dppy)] ( 1 b ) and [Au2Ag(μ‐mes)2(μ‐dppe)][SO3CF3] ( 3 a ) were determined by a single‐crystal X‐ray diffraction study. 3 a in solid state is not a cyclic trinuclear Au2Ag derivative but it gives an open polymeric structure instead, with the {Au2(μ‐dppe)} fragments “linked” by {Ag(μ‐mes)2} units. The very short distances of 2.7559(6) Å (Au? Ag) and 2.9229(8) Å (Au? Au) are indicative of gold–silver (metallophilic) and aurophilic interactions. A systematic study of their luminescence properties revealed that all compounds are brightly luminescent in solid state, at room temperature (RT) and at 77 K, or in frozen DMSO solutions with lifetimes in the microsecond range and probably due to the self‐aggregation of [Au2M(μ‐mes)2(μ‐LL)]+ units (M=Ag or Cu; LL=dppe or dppy) into an extended chain structure, through Au? Au and/or Au? M metallophilic interactions, as that observed for 3 a . In solid state the heterometallic Au2M complexes with dppe ( 2 a – 4 a ) show a shift of emission maxima (from ca. 430 to the range of 520‐540 nm) as compared to the parent dinuclear organometallic product 1 a while the complexes with dppy ( 2 b–4 b ) display a more moderate shift (505 for 1 b to a max of 563 nm for 4 b ). More importantly, compound [Au2Ag(μ‐mes)2(μ‐dppy)]ClO4 ( 2 b ) resulted luminescent in diluted DMSO solution at room temperature. Previously reported compound [Au2Cl2(μ‐LL)] (LL dppy 5 b ) was also studied for comparative purposes. The antimicrobial activity of 1–5 and Ag[A] (A=ClO4?, SO3CF3?) against Gram‐positive and Gram‐negative bacteria and yeast was evaluated. Most tested compounds displayed moderate to high antibacterial activity while heteronuclear Au2M derivatives with dppe ( 2 a – 4 a ) were the more active (minimum inhibitory concentration 10 to 1 μg mL?1). Compounds containing silver were ten times more active to Gram‐negative bacteria than the parent dinuclear compound 1 a or silver salts. Au2Ag compounds with dppy ( 2 b , 3 b ) were also potent against fungi. 相似文献
128.
129.
Abir Ben Bacha Islem Abid Habib Horchani 《Applied biochemistry and biotechnology》2012,168(5):1277-1287
Stingray phospholipase A2 group IIA (SPLA2-IIA) was recently isolated and purified to homogeneity from the intestine of the common stingray Dasyatis pastinaca, suggesting that this enzyme plays an important role in systemic bactericidal defense. The present study showed that SPLA2-IIA was highly bactericidal against Gram-positive bacteria with inhibition zones and minimal inhibitory concentration values in the range of 13–25 mm and 2–8 μg/ml, respectively, whereas Gram-negative bacteria exhibited a much higher resistance. The bactericidal efficiency of SPLA2-IIA was shown to be unaffected by high protein and salt concentrations, but dependent upon the presence of calcium ions, and then correlated to the hydrolytic activity of membrane phospholipids. Importantly, we showed that stingray phospholipase A2 group IIA presents no cytotoxicity after its incubation with MDA-MB-231 cells. SPLA2-IIA may be considered as a future therapeutic agent against bacterial infections. 相似文献
130.
A simple, rapid and sensitive method based on microextraction in packed syringe (MEPS), in combination with gas chromatography–mass spectrometry (GC–MS) was developed. Polyaniline (PANI) nanowires network was synthesized and used as sorbent of MEPS for the multiresidue determination of selected analytes from triazine, organochlrorine and organophosphorous pesticides in aqueous samples. The PANI nanowires network was prepared using soft template technique and its characterization was studied by scanning electron microscopy (SEM). The presence of micelles in this methodology showed to be an important parameter in shaping the growing polymer. Hexadecyltrimethylammonium bromide (HTAB) was used as structure directing agent in PANI preparation procedure and this was led to the formation of nanowires with diameters ranging from 35 nm to 45 nm. The synthesized PANI nanowires network showed higher extraction capability in comparison with the bulk PANI. Important parameters influencing the extraction and desorption processes including desorption solvent, elution volume, draw–eject cycles of sample, draw–eject mode, pH effect and amount of sorbent were optimized. Limits of detection were in the range of 0.07–0.3 ng mL−1 using time scheduled selected ion monitoring (SIM) mode. The linearity of method was in the range from 0.5–200 ng mL−1 to 0.2–1000 ng mL−1. The method precision (RSD %) with three replicates were in the range of 5.3–18.4% at the concentration level of 5 ng mL−1. The developed method was successfully applied to the Zayandeh-rood river water samples and the matrix factor obtained for the spiked real water samples were in the range of 0.79–0.94. 相似文献