48 research outputs found
Enzyme-induced Formation of ß-Lactoglobulin Fibrils by AspN Endoproteinase
No full textThis paper describes a low temperature, enzymatic route to induce fibrillar structures in a protein solution. The route comprises two steps. First, ß-lactoglobulin was hydrolyzed into peptides at pH 8 and 37°C with the enzyme AspN endoproteinase, which resulted in the formation of random aggregates. After hydrolysis, the pH was lowered to 2. As a result, long fibrillar aggregates were formed which was observed using transmission electron microscopy and Thioflavin T fluorescence measurements
A novel measurement technique to estimate the RF beat-linewidth of free-running heterodyning system using a photonic discriminator
No full textWe propose a novel technique to our knowledge to estimate the beat spectrum linewidth of a free-running heterodyning scheme using an optical discriminator. Utilizing a dense wavelength division multiplexing (DWDM) filter as an optical discriminator, the phase modulation (PM) to intensity modulation (IM) conversion is achieved. Thus converted phase noise of the laser into RIN (relative intensity noise). We establish a relationship between the converted RIN and the beat spectrum linewidth. The proposed concept on beat spectrum linewidth estimation is demonstrated and compared with direct beat spectrum measurement. We show that our proposed technique estimates the beat linewidth more accurately for a free-running heterodyning scheme
Formation of a rhodium(II) monohydrido complex derived from wilkinson's complex RhCl(PPh3)3 in the interlamellar spaces of montmorillonite and catalytic hydrogenation of cyclohexene
No full textMultiwavelength optical beam forming network with ring resonator-based binary-tree architecture for broadband phased array antenna systems
No full textIntegrated optical beam forming networks (OBFNs) offer many advantages for phased array applications. ORR-based true-time-delay units can be cascaded in a binary tree topology and tuned for continuously-adjustable broadband time delay. Nonetheless, with large number of antenna elements, the OBFN may become very complex. A novel idea is proposed to exploit the frequency periodicity of the ORRs and the WDM technique to achieve multiple-signal-paths on a single beamformer, thus reducing complexity and costs. The use of high index contrast waveguides in Si-compatible technology further reduces chip footprint and allows the use of integrated OBFNs for large arrays and multi-beam applications
Thermodynamics of homogeneous hydrogenation: Part VII. Thermodynamics of the homogeneous hydrogenation of cyclohexene catalyzed by some water-soluble ruthenium complexes containing π-acidic ligands
No full textThe complexes K[Ru(EDTA-H)Cl]2H2O 1, [Ru(EDTA-H)(PPh3)] 2, K[Ru(EDTA-H)(CO)] 3 and K[Ru(EDTA-H)(SnCl3−)] 4 activate molecular hydrogen at 30°C and 1 atm H2 in 7:3 alcoholrwater mixture by heterolytic cleavage of the H-H bond to form the thermodynamically stable hydrido complexes [Ru(EDTA-H)(H)]2−5, [Ru(EDTA-H)(PPh3)(H)]2−6, [Ru(EDTA-H)(CO)(H)]2−7 and [RutEDTA-H)(SnCl3−(H)]3−8 in solution characterized by their proton NMR in situ. Complexes 6-8 form isomeric hydrides where H iscis or trans to the π-acidic group L (L = PPh3, CO, SnCl3−), the cis species being predominant in solution. The hydrido proton peaks in complexes 5-8 shift downfield in the order 4 > 3 > 2 > 1, in accord with the decreasing π-acidity of the coordinated group. The homogeneous hydrogenation of cyclohexene catalyzed by complexes 1-4 was investigated in the temperature range 10-40°C at 0.4-1 atm of H2 partial pressure. Thermodynamic parameters corresponding to the formation of the monohydrido complexes 5-8 and the monoolefin complexes 1-5 were computed. The activation parameters corresponding to the rate constants K1 and K2 for the homogeneous hydrogenation of cyclohexene were also calculated. The enthalpy of the formation of hydrido and olefin complexes decreases with an increase in the π-acidity of the coordinated ligand. The entropies of the hydride and olefin complex formation are large positive numbers, indicating either the dissociation of a Cl− from the coordination sphere of the metal ion in 1, or removal of a coordinated carboxylate group from the coordination positions of EDTA to accommodate H− or olefin. The catalytic activity of complexes 1-4 decreases in the order 4 > 3 > 2 > 1, in line with the decreasing π-acidity of the secondary group L coordinated to Ru(II). The thermodynamic parameters corresponding to the steps K1 and K2 show small exothermic values for ΔH‡ and large negative values for ΔS‡. The slow step K1 is the predominant step for the catalytic transfer of hydride proton to the olefin. There is a correlation between ΔH‡ of path A (K1) , ΔH0 of hydride formation and ΔS‡ and the hydride proton shift δ (ppm), indicating the involvement of the hydride in the rate-determining step
Phase noise analysis of an rf local oscillator signal generated by optical heterodyning of two lasers
No full textWe investigate a way of generating an RF local oscillator (LO) signal by means of optical heterodyning of two lasers. This LO signal will be used to down-convert a Ku-Band(10.7 GHz12.75 Ghz)RF signal from a phased array antenna (PAA) to an intermediate frequency 950 MHz to 3 GHz) at the mixer. In this paper we have modeled the laser spectrum perturbed by phase noise. In addition, we analyze the impact of the lasers phase noise on the quality of the gererated LO by optical heterodyning
Kinetics of the formation of μ-peroxo bis(ethylene-diaminetetraacetate)-ruthenate(IV) By the reaction of H<SUB>2</SUB>O<SUB>2</SUB> with ethylenediaminetetraacetate-ruthenate(III) complex
No full textThe kinetics of interaction of H2O2 with K[Ru(H-EDTA)Cl] at pH=3.0, μ=0.1 M (NaClO4) was studied using stopped-flow spectrophotometry. The formation of the μ-peroxo complex was investigated at λmax=390 nm. The reaction was found to be first order with respect to the metal complex and hydrogen peroxide concentrations. The activation parameters were computed and a mechanism is proposed for the formation of the μ-peroxo complex
Analysis of phase noise and cnr degradation of externally generated lo signal in lnb for ku-band dvb-s systems by heterodyning two lasers
No full textWe investigate the externally generation of an LO signal by optical heterodyning, which is then distributed to each of the mixers at every antenna element of a phased array antenna used for standard DVB-S (digital Video Broadcasting-Satellite) reception system. The system1 is presented in Figure 1. The Ku-Band (10.7 GHz ~12.75 GHz) RF signal from the antenna array is amplified and then down converted to IF (950 MHz to 2150 MHz) at the mixer by a 9.75 GHz LO signal generated by optical heterodynin
Ring resonator-based integrated photonic beam former for phased array antennas
No full textIn this article we introduce one of the microwave photonics techniques being researched in our group, namely integrated photonic beam former for phased array antennas. The photonic beam former operates with true time delays achieved by means of integrated optical ring resonator filters. Compared to the conventional electrical beam former, this photonic solution provides the advantages of large instantaneous bandwidth, small size, light weight, low loss, and immunity to electromagnetic interference. The bandwidth configurability and continuous delay tunability of the optical ring resonator-based delay elements allow the phased array antenna to perform squint-free and seamless beam steering for broadband applications such as mobile Ku-band satellite communication and gigahertz-bandwidth radio telescope
