Modelling gross primary production of a tropical semi-deciduous forest in the southern Amazon Basin

Semi-deciduous forest in the Amazon Basin is sensitive to temporal variation in surface water availability that can limit seasonal rates of leaf and canopy gas exchange. We estimated the seasonal dynamics of gross primary production (GPP) over 3 years (2005–2008) using eddy covariance and assessed canopy spectral reflectance using MODIS imagery for a mature tropical semi-deciduous forest located near Sinop, Mato Grosso, Brazil. A light-use efficiency model, known as the Vegetation Photosynthesis Model (VPM), was used to estimate seasonal and inter-annual variations in GPP as a function of the enhanced vegetation index (EVI), the land surface water index (LSWI), and local meteorology. Our results indicate that the standard VPM was incapable of reproducing the seasonal variation in GPP, primarily because the model overestimated dry-season GPP. In the standard model, the scalar function that alters light-use efficiency (ε_g) as a function of water availability (W_scalar) is calculated as a linear function of the LSWI derived from MODIS; however, the LSWI is negatively correlated with several measures of water availability including precipitation, soil water content, and relative humidity (RH). Thus, during the dry season, when rainfall, soil water content, and RH are low, LSWI, and therefore, W_scalar, are at a seasonal maximum. Using previous research, we derived new functions for W_scalar based on time series of RH and photosynthetic photon flux density (PPFD) that significantly improved the performance of the VPM. Whether these new functions perform equally well in water stressed and unstressed tropical forests needs to be determined, but presumably unstressed ecosystems would have high cloud cover and humidity, which would minimize variations in W_scalar and GPP to spatial and/or temporal variation in water availability.     

Determination of water content in Brazilian honeybee-collected pollen by Karl Fischer titration

This paper assesses the performance of a chemical method based on the Karl Fischer titration to determine the water content in samples of dehydrated honeybee-collected pollen. The following analysis parameters were investigated: extraction temperature, particle size, reaction time, and weight of a dried pollen sample. After optimization, the method was used to determine the water content of 154 samples of dried honeybee-collected pollen from different geographical regions of Brazil. The Karl Fischer titration method, performed using a solvent mixture of methanol and n-octanol (1:1 v/v) at 50 °C on pollen particles 600 μm in size produced the best results. Mean values for water content of the 154 samples of dried honeybee-collected pollen from 12 Brazilian regions ranged from 3% to 9%.     

Computer simulation and SERR detection of cytochrome c dynamics at SAM-coated electrodes

In this paper we present a combined experimental and theoretical study of the heterogeneous electron transfer reaction of cytochrome c electrostatically adsorbed on metal electrodes coated with monolayers of 6-mercaptohexanoic acid. Molecular dynamics simulations and pathways calculations show that adsorption of the protein leads to a broad distribution of orientations and, thus, to a correspondingly broad distribution of electron transfer rate constants due to the orientation-dependence of the electronic coupling parameter. The adsorbed protein exhibits significant mobility and, therefore, the measured reaction rate is predicted to be a convolution of protein dynamics and tunnelling probabilities for each orientation. This prediction is confirmed by time-resolved surface enhanced resonance Raman which allows for the direct monitoring of protein (re-)orientation and electron transfer of the immobilised cytochrome c. The results provide a consistent explanation for the non-exponential distance-independence of electron transfer rates usually observed for proteins immobilized on electrodes.     

Development of Low-Cost Remote-Control Generators Based on BiTe Thermoelectric Modules

This paper presents a new thermogenerator based on moderate-temperature (up to 175°C) BiTe modules available on the open market. Despite this handicap relative to commercial thermogenerators based on high-temperature proprietary-technology PbBi modules (up to 560°C), this new design may become economically competitive due to its innovative thermal sink. Our thermal sink is based on a free-convection water loop built with standard tubing and household hot-water radiators, leading to a more practical, modular design. So, the specific cost of about 55,000 USD/kW obtained for this 120-W prototype is improved to 33,000 USD/kW for a 1-kW unit, which represents about half the price of commercial thermogenerators. Moreover, considering recently launched BiTe modules (that withstand up to 320°C), our proposition could have an even more favorable outlook.     

A congruence rule format for name-passing process calculi

We introduce a GSOS-like rule format for name-passing process calculi. Specifications in this format correspond to theories in nominal logic. The intended models of such specifications arise by initiality from a general categorical model theory. For operational semantics given in this rule format, a natural behavioural equivalence—a form of open bisimilarity—is a congruence.     

Antinucleating action of polystyrene on the isothermal cold crystallization of poly(ethylene terephthalate)

The effect of polystyrene (PS) on the kinetics of the cold crystallization of poly(ethylene terephthalate) (PET) was thoroughly investigated. The PET/PS blends were essentially immiscible, as observed by dynamic mechanical thermal analysis, which showed two distinct glass‐transition temperatures, and by scanning electron microscopy. The neat PET and its blends were isothermally cold‐crystallized at various temperatures, and the kinetic parameters were determined with the Avrami approach. PET and its blends presented values of the Avrami exponent close to 2, and the kinetic constant increased with the crystallization temperature increasing. For all the crystallization temperatures studied, the presence of only 1 wt % PS significantly reduced the rate of cold crystallization of PET. A further increase in the PS concentration did not show any significant influence. The blends presented higher values of the activation energy for cold crystallization, which was estimated from Arrhenius plots. The equilibrium melting temperature of neat PET was determined on the basis of the linear Hoffman–Weeks extrapolative method to be ～ 255°C. This value decreased in the presence of PS, and this suggested limited solubility between PET and PS. From the spherulitic growth equation proposed by Hoffman and Lauritzen, the nucleation parameter was obtained, and it was shown to be higher for the neat PET than for the blends. Moreover, a transition of regimes (I → II) was observed in both PET and its blends. From the investigations conducted here, it is clear that PS in small amounts causes a reduction in the rate of PET crystallization, acting as an antinucleating agent. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Online Identification of Horizontal Two-Phase Flow Regimes Through Gabor Transform and Neural Network Processing

The fundamental objective of this work is the development of a specialist system capable of diagnosing different configurations of horizontal two-phase flow regimes. It is important to emphasize that this knowledge is of capital importance to the efficient operation of facilities for the manipulation and transportation of multiphase fluids, and it represents one of the most important challenges in petrochemical and thermonuclear industries today. The working principle of the proposed methodology is based on the signals acquired by a rapid response pressure gradient sensor and their decomposition into Gabor coefficients, followed by processing through a previously trained artificial neural network. The implementation is accomplished in such a way that the diagnosis operation is performed online, from the acquisition of the signal to its post-processing. An experimental campaign was conducted at the facilities of the Thermal and Fluids Engineering Laboratory (NETeF) at the University of São Paulo in order to validate the proposed methodology. Experimental pressure gradient signals were obtained for all main horizontal air-water flow regimes (stratified smooth, stratified wavy, intermittent, annular, and bubbly) produced in a 12 m long test section with an internal diameter of 30 mm. Results show that the percentage of correct flow regime diagnosis in steady-state conditions is practically 100%, provided the detection level is adequately set.     

Large eddy simulation of pollen transport in the atmospheric boundary layer

This paper presents a framework to simulate pollen dispersal by the wind based on the large eddy simulation (LES) technique. Important phenomena such as the pollen emission by the plants and the ground deposition are parameterized by the lower boundary condition. The numerical model is validated against previously published experiments of point source releases of glass beads and pollen grains in the atmospheric boundary layer. The numerical model is used together with experimental data of pollen emission and downwind deposition from a natural field obtained near Washington, DC, in the summer of 2006. The combined analysis of experimental and numerical data allows to elucidate the emission/transport/deposition process in considerable detail. In particular, the relative fractions of pollen deposited inside the source field and airborne at the edge of the field can be quantified. The use of LES allows quantification of important intermittent deposition events far from the source field.     

Polycrystalline fluorine-doped tin oxide as sensoring thin film in EGFET pH sensor

The Extended Gate Field Effect Transistor (EGFET) is a device composed of a conventional ion-sensitive electrode and a MOSFET device, which can be applied for the measurement of ion content in a solution. The EGFET is fabricated connecting the sensitive membrane to a commercial MOSFET. We investigated the use of fluorine-doped tin oxide films (FTO) as sensitive membrane to EGFET. The commercial FTO shows a low resistivity and a crystalline structure, both determined using conductivity set-up and X-ray diffraction experiments, respectively. So far, it has been known that an amorphous structure is desirable to obtain high sensitivity. Despite of the a crystalline structure, we have fabricated the FTO as EGFET for pH sensor and carried out experiments in order to obtain the response of the device inserted into solutions with pH values from 2 up to 12. In this range, we have quantified a sensitivity of 50 mV/pH, which may have large potential applications as pH and biosensors. In addition, both the film and the structure of the sensor are cheaper and easier to make than in common techniques.