Numerical results on some generalized random Fibonacci sequences

Random Fibonacci sequences are stochastic versions of the classical Fibonacci sequence $f_{n+1}=f_n+f_{n?1}$ for $n>0$, and $f_0=f_1=1$, obtained by randomizing one or both signs on the right side of the defining equation and/or adding a “growth parameter.” These sequences may be viewed as coming from a sequence of products of i.i.d. random matrices and their rate of growth measured by the associated Lyapunov exponent. Following the techniques presented by Embree and Trefethen in their numerical paper Embree and Trefethen (1999) [2], we study the behavior of the Lyapunov exponents as a function of the probability $p$ of choosing $+$ in the sign randomization.     

Progress and Perspectives of Thin Film Kesterite Photovoltaic Technology: A Critical Review

The latest progress and future perspectives of thin film photovoltaic kesterite technology are reviewed herein. Kesterite is currently the most promising emerging fully inorganic thin film photovoltaic technology based on critical raw‐material‐free and sustainable solutions. The positioning of kesterites in the frame of the emerging inorganic solar cells is first addressed, and the recent history of this family of materials briefly described. A review of the fast progress achieved earlier this decade is presented, toward the relative slowdown in the recent years partly explained by the large open‐circuit voltage (V_OC) deficit recurrently observed even in the best solar cell devices in the literature. Then, through a comparison with the close cousin Cu(In,Ga)Se₂ technology, doping and alloying strategies are proposed as critical for enhancing the conversion efficiency of kesterite. In the second section herein, intrinsic and extrinsic doping, as well as alloying strategies are reviewed, presenting the most relevant and recent results, and proposing possible pathways for future implementation. In the last section, a review on technological applications of kesterite is presented, going beyond conventional photovoltaic devices, and demonstrating their suitability as potential candidates in advanced tandem concepts, photocatalysis, thermoelectric, gas sensing, etc.     

Use of image analysis in the study of competition between filamentous and non-filamentous bacteria

One of the most common problems in the operation of activated sludge plants is the inability to separate solids from treated effluents in the clarifiers caused by the overgrowth of filamentous micro-organisms (FM) with respect to floc-forming bacteria. In order to develop kinetic models that help to predict bulking events, growth kinetics of the FMs and non-filamentous bacteria (NFB) should be known. This paper addresses the competition of a FM and a NFB in a continuous stirred tank reactor. Experimental observations of the effect of the dilution rate on the composition of the mixed culture were compared to simulated results. Image analysis was used to measure NFB and FM fractions in order to evaluate the proposed mathematical model. Experimental results and numerical simulations showed that low D values favored the growth of FM; on the contrary, when high D values were applied a rapid overgrowth of the NFB were observed. Thus, high D values favored the growth of NFB minimizing the risk of filamentous bulking.     

Transgenic corn seed for recombinant protein production: relevant aspects on the aqueous extraction of native components

Plants have been considered one of the most promising expression systems for the production of recombinant proteins. Foreseen advantages include high productivity, optimal processing and assembly, and the non‐propagation of human or animal pathogens. A few successful examples of commercial proteins produced in plants have been reported in the literature, such us β‐glucoronidase, avidin, hirudin and aprotinin. Although the purification scheme is always a challenge in downstream processing development, the extraction is the key point since the presence of impurities deleterious to the process efficiency and operational‐life span of the equipment is determined at this step. This work reports the effect of pH and ionic strength in the extraction of proteins, phenolic compounds, lipids and sugars from transgenic corn seed. The phenolic compounds, lipids and reducing sugars were not significantly affected by changes in the ionic strength of the extracting solutions in the range 0–300 mM NaCl and pH 6.3. However, at high pH value (pH 10.0), high solubilization of proteins, phenolic compounds and lipids was achieved, whereas reducing sugars were not significantly extracted at this condition. This work is complementary to the studies reported in a previous paper and contributes to the development of recombinant protein recovery and purification process from transgenic corn. Copyright © 2004 Society of Chemical Industry     

Demonstration of a low bandwidth 1.06 μm optical phase-lockedloop for coherent homodyne communication

A type-II, 1.06-μm, optical phase-locked-loop (OPLL) for use in a coherent homodyne receiver is discussed. Diode-laser-pumped solid-state lasers are used for both the local oscillator and transmitter, because their phase noise is significantly lower than that of diode lasers. Closed-loop RMS phase noise of less than 12 mrad (0.69°) is achieved, and modulation-demodulation in bulk modulators at rates from 20 kHz to 20 MHz with less than 19° of modulation depth is demonstrated