The Role of F-Box Proteins during Viral Infection

The F-box domain is a protein structural motif of about 50 amino acids that mediates protein–protein interactions. The F-box protein is one of the four components of the SCF (SKp1, Cullin, F-box protein) complex, which mediates ubiquitination of proteins targeted for degradation by the proteasome, playing an essential role in many cellular processes. Several discoveries have been made on the use of the ubiquitin–proteasome system by viruses of several families to complete their infection cycle. On the other hand, F-box proteins can be used in the defense response by the host. This review describes the role of F-box proteins and the use of the ubiquitin–proteasome system in virus–host interactions.     

A Comprehensive Study of Particle Size Distributions with the Use of PostInjection Strategies in DI Diesel Engines

Control strategies such as variations in injection pressure and timing have been used by researchers to reduce in-cylinder exhaust emissions and meet legislation standards. Postinjection has been studied for several years and is now well known as an efficient strategy for reducing soot emission. Diesel gaseous and particle mass emissions have been progressively reduced over the last twenty years as a consequence of increasingly restrictive emission legislation and the application of aftertreatment devices. The main objective of this work is to better understand the effect of postinjection on particle size distribution in diesel exhaust. The approach uses a modern, well-instrumented research engine test cell equipped with a flexible high pressure fuel injection system. The results of this work provide guidelines for developing strategies to reduce particle size distribution in diesel engines. A major improvement in particle size distribution was found in the accumulation mode by using a close postinjection of a small quantity of fuel. For reduction in nucleation mode, a relationship was found with close postinjections of large quantities of fuel.     

Fixation of Chromium in Wood from Dichromate and Chromate Salt Solutions

It has been reported that treatment of wood surfaces with aqueous solutions of chromium trioxide imparts some beneficial properties like weather resistance and some degree of water repellency. The work presented here aims at finding alternative ways of fixing chromium in wood with the avoidance of the very acidic and strong oxidant conditions of chromic acid solutions. This is because these solutions may affect the strength of wood, and are known to have a very high human toxicity. In this study, chromium has been fixed into wood from hexavalent chromium solutions at pH's of ～1.5 (CrO₃ aq.), ～3.8–3.9 (K₂Cr₂O₇ aq.) and ～9.5–10.3 (K₂CrO₄ aq.). For the CrO₃-solutions the effects of temperature and reaction time on the fixation of chromium were investigated. For the dichromate and chromate solutions, fixation experiments were carried out with Cr-concentration and reaction times as variables. It is shown that a 3%-fixation level of chromium in small wood specimens can be attained from dichromate and chromate solutions without significant mechanical damage to wood. On the other hand, even diluted CrO₃-solutions (0.01 M) impart serious strength reductions in wood at temperatures of 90° C and higher when reacted for 8 hours, and the chromium content of wood resulting from such treatment is of the order of only 1%.     

Study of Visibility Degradation Due to Coagulation,Condensation, and Gravitational Settling of the Atmospheric Aerosol

This work studies the evolution in time of the light extinction coefficients of the single-component spherical aerosols after a given mechanism of removal (coagulation, heterogeneous nucleation, and gravitational settling) as a function of time. The well-known equations of scavenging are applied to 3 atmospheric environments (clear, hazy, and urban) that represent the aerosol particle size distributions (PSDs) in the countryside, the industry, and the city, respectively. The aerosol scattering and absorption coefficients are determined from the single particle light extinction efficients, K s ( m , p ) and K a ( m , p ), where m is the complex refractive index of each particle and p = ~ D p / u , the dimensionless parameter relating the particle diameter D p to the wavelength u of the incident light. The single particle light extinction efficiences K s and K a can be derived theoretically by Mie's solution to Maxwell's equations (van de Hulst 1981; Kerker 1969). From this study it is inferred that gravitational settling predominates with respect to coagulation and condensation since the visual range is increased considerably. Besides, gravitational settling is the main mechanism for removal of respirable aerosol in comparison to condensation and coagulation and is close to 6 times better than rainout (García Nieto et al. 1994).     

Soft solution fluorine-free synthesis of anatase nanoparticles with tailored morphology

TiO₂ nanoparticles with tailored morphology have been synthesized under exceptionally soft conditions. The strategy is based on the use of a non-aqueous alcoholic reaction medium in which water traces, coming either from the air (atmospheric water) or from an ethanol–water azeotropic mixture (ethanol 96%), are incorporated in order to accelerate hydrolysis of the Ti–precursor. Moreover, organic surfactants have been used as capping agents so as to tailor crystal growth in certain preferential directions. Combinations of oleic acid and oleylamine, which lead to the formation of another surfactant, dioleamide, are employed instead of fluorine-based compounds, thus increasing the sustainability of the process. As a result, TiO₂ nanostructured hierarchical microspheres and individual nanoparticles with exposed high-energy facets can be obtained at atmospheric pressure and temperatures as low as 78 °C.     

A complex biological system: the fly's visual module

Is the characterization of biological systems as complex systems in the mathematical sense a fruitful assertion? In this paper we argue in the affirmative, although obviously we do not attempt to confront all the issues raised by this question. We use the fly's visual system as an example and analyse our experimental results of one particular neuron in the fly's visual system from this point of view. We find that the motion-sensitive 'H1' neuron, which converts incoming signals into a sequence of identical pulses or 'spikes', encodes the information contained in the stimulus into an alphabet composed of a few letters. This encoding occurs on multilayered sets, one of the features attributed to complex systems. The conversion of intervals between consecutive occurrences of spikes into an alphabet requires us to construct a generating partition. This entails a one-to-one correspondence between sequences of spike intervals and words written in the alphabet. The alphabet dynamics is multifractal both with and without stimulus, though the multifractality increases with the stimulus entropy. This is in sharp contrast to models generating independent spike intervals, such as models using Poisson statistics, whose dynamics is monofractal. We embed the support of the probability measure, which describes the distribution of words written in this alphabet, in a two-dimensional space, whose topology can be reproduced by an M-shaped map. This map has positive Lyapunov exponents, indicating a chaotic-like encoding.