Dynamics of indigenous yeast populations during spontaneous fermentation of wines from Mendoza, Argentina

Fermentation of wine is a complex microbial reaction, which involves the sequential development of various species of yeasts and lactic acid bacteria. Of these, yeasts are the main group responsible for alcoholic fermentation. The aim of this work was to study, under industrial conditions, the evolution of yeast populations and to describe the individual evolution of the most important yeasts during three spontaneous fermentations of Malbec musts from Argentina. This work shows the significant participation of non-Saccharomyces yeasts during spontaneous fermentation of musts, with the ubiquitous presence of three main species: Kloeckera apiculata, Candida stellata and Metschnikowia pulcherrima.     

Operating reserve determination and its influence on the operating costs of interconnected power systems

A methodology to carry out reliability studies to compute operating reserve requirements of interconnected systems is formulated.This paper shows the application of developments carried out at ‘Instituto de Energía Eléctrica’ in order to calculate the operating reserve requirements, their composition in relation to the access times of different kinds of reserve, and the influence that equipment variations will have on the electric power system operation costs.The calculation of power interchange between areas is performed with a stochastic model of the system. In this model the different levels of assistance capacity of each area are associated with their occurrence probabilities. Covering of own demand has priority. Interconnecting lines between areas are modeled by probabilities associated with their possible states.This methodology allows adequate consideration of operating conditions in power systems planning. System optimal operation costs are calculated under the constraint that there is sufficient operating reserve (stand-by plus spinning reserve) to guarantee a given reliability level.The main aim of this work was the application of this methodology to the Sistema Nacional Interconectado Argentino (Argentine National Interconnected System) for assessing a first approach to operating reserve composition and requirements. In addition, the influence on the operating costs of including a pumped storage power plant located in the province of Buenos Aires is evaluated.     

Nanospheres Containing Urea: Photothermic Properties

In the present research, nanospheres of chitosan (CS), maltodextrin, and sodium tripolyphosphate (STPP), loaded with urea, were synthesized by using an ionic gelation technique. In the nanosphere synthesis was used a central composite experimental design, obtaining nanospheres with an average size of 275?±?32 nm and 27.5 mV zeta potential. The nanospheres were characterized by their hydrodynamic diameter, polydispersity index, nitrogen content, and thermal properties such as thermal diffusivity (α), effusivity (e), and conductivity (k); also melting temperature was obtained by differential scanning calorimetry. The thermal properties of nanospheres show that the sample with the smallest size has a thermal diffusivity value of (14.4?±?0.4)?×?10^?8 m²·s^?1 and a thermal conductivity value of (6.4?±?0.1)?×?10^?1 W·m^?1·K^?1, and the obtained melting temperature was 157 °C. Higher concentrations of CS increase the values of these thermal properties, probably because chitosan interacts ionically with STPP forming a reticular network due to the opposite charges of both molecules.     

Probabilistic Boolean network modeling of an industrial machine

Theoretical modeling of manufacturing processes assists the design of new systems for predictions of future behavior, identifies improvement areas, and evaluates changes to existing systems. A novel approach is proposed to model industrial machines using probabilistic Boolean networks (PBNs) to study the relationship between machine components, their reliability and function. Once a machine is modeled as a PBN, through identification of regulatory nodes, predictors and selection probabilities, simulation and property verification are used to verify model correctness and behavior. Using real machine data, model parameters are estimated and a PBN is built to describe the machine, and formulate valid predictions about probability of failure through time. Two models were established: one with non-deterministic inputs (proposed), another with components’ MTBFs inputs. Simulations were used to generate data required to conduct inferential statistical tests to determine the level of correspondence between predictions and real machine data. An ANOVA test shows no difference between expected and observed values of the two models (p value = 0.208). A two-sample T test demonstrates the proposed model provides values closer to expected values; consequently, it can model observable phenomena (p value \(=\) 0.000). Simulations are used to generate data required to conduct inferential statistical tests to determine the level of correspondence between model prediction and real machine data. This research demonstrates that using PBNs to model manufacturing systems provides a new mechanism for the study and prediction of their future behavior at the design phase, assess future performance and identify areas to improve design reliability and system resilience.     

Smooth interfaces for spectral element method for the solution of incompressible Newtonian fluid flow

A smoothing technique is developed to calculate the interface conditions of spectral element method for solving the incompressible Newtonian fluid flow. The first derivative at the interface of spectral elements is calculated by using only the adjacent subdomains. Numerical simulations of an incompressible laminar fluid flow through a planar channel and a 2:1 planar contraction channel are presented for various Reynolds numbers.

The effects of impoundment and non‐native species on a river food web in Mexico's central plateau

Habitat modifications, non‐native species and other anthropogenic impacts have restructured fish communities in lotic ecosystems of central Mexico. Conservation of native fishes requires understanding of food web changes resulting from the introduction of non‐native species, flow alteration and other human impacts. Using δ¹³C and δ¹⁵N analysis of fishes and invertebrates we investigated the effects of non‐native species, and reservoirs on food webs of the Laja river ecosystem (Guanajuato, central Mexico). We estimated trophic position (TP), relative trophic niche and food web dispersion at 11 reservoir, river and tailwater sites. Reservoirs and non‐native fishes modified food webs in the Laja. Food web dispersion was greater in reservoir than in tailwater and river sites. Reservoir food webs had the greatest range of δ¹³C values, indicating a more diverse resource base compared to rivers. δ¹³C values increased with distance downstream from reservoirs, suggesting declining subsidies of river food webs by reservoir productivity. Stable isotopes revealed potential effects of non‐native fishes on native fishes via predation or competition. Non‐native Micropterus salmoides were top predators in the system. Non‐natives Cyprinus carpio, Oreochromis mossambicus and Carassius auratus exhibited lowest TP in the Laja but overlapped significantly with most native species, indicating potential for resource competition. Native Chirostoma jordani was the only species with a significantly different trophic niche from all other fish. Many rivers in central Mexico share similar anthropogenic impacts and similar biotas, such that food web patterns described here are likely indicative of other river systems in central Mexico. Copyright © 2008 John Wiley & Sons, Ltd.     

Impact of solder pad size on solder joint reliability in flip chipPBGA packages

A variety of parameters impact package reliability. One set of parameters that does not get much attention is the variations in package design that are assembly and vendor related. This study shows that solder pad size is important in solder joint reliability. Differences in solder pad size due to different vendors and processes can affect the reliability considerably. The impact of substrate thickness on package reliability has been shown in finite element stress analysis, moire interferometry experiments, and reliability tests. However, in certain cases, the pad size effect can be so significant that it overrides the impact of substrate thickness. This work indicates that in order to obtain good correlation between predictive engineering results and reliability tests data, this factor should not be ignored. In this study, finite element simulation has been used to quantify the pad size effect on the BGA reliability in the PBGA package. Air-to-air thermal cycling test results were compared with FEM predictions. Optimized pad sizes are discussed and the impact on the solder joint reliability is predicted. Solder pad size effect was found to be a dominant feature in correlating test data with predictions     

Glycerol polymerization degree effect on the emulsifying properties of polyglycerol esters

Polymeric emulsifiers based on glycerol and oleic acid were developed and their properties evaluated in palm oil and water solutions. Developed polymeric emulsifiers were polyglycerol-esters. Polymerization degree of polyglycerol-esters at different dosages (from 0.2 to 3% w/v) had a significant effect over emulsion stability, water surface tension, droplet size, and viscosity. Polyglycerol-ester with highest polymerization degree behaved more efficiently as emulsifier. A dosage of 0.5% w/v was required to maintain emulsion stability for a half-life period of 872 min (~14.5 h); which, is 5.6 and 3.6-fold longer stability than with the other two polyglycerol-esters developed. When dosage increased to 3% w/v, the emulsion stability also increased to 3792 min (~2.6 days). Nevertheless, surfactants with lower polymerization degree and molecular weight did not behave the same way. Emulsifier with highest polymerization degree reduced water surface tension by 70% and the mean particle diameter decreased when emulsifier polymerization degree increased. For the viscosity parameter, there were two interesting regions: for shear rates up to 1 s⁻¹ the emulsion behaved as Non-Newtonian fluid type Shear-thinning; while, higher shear rates, the viscosity exhibited a Newtonian profile.     

Modeling preventive maintenance of manufacturing processes with probabilistic Boolean networks with interventions

Recent developments in intelligent manufacturing have validated the use of probabilistic Boolean networks (PBN) to model failures in manufacturing processes and as part of a methodology for Design Failure Mode and Effects Analysis (DFMEA). This paper expands the application of PBNs in manufacturing processes by proposing the use of interventions in PBNs to model an ultrasound welding process in a preventive maintenance (PM) schedule, guiding the process to avoid failure and extend its useful work life. This bio-inspired, stochastic methodology uses PBNs with interventions to model manufacturing processes under a PM schedule and guides the evolution of the network, providing a new mechanism for the study and prediction of the future behavior of the system at the design phase, assessing future performance, and identifying areas to improve design reliability and system resilience. A process engineer designing manufacturing processes may use this methodology to create new or improve existing manufacturing processes, assessing risk associated with them, and providing insight into the possible states, operating modes, and failure modes that can occur. The engineer can also guide the process and avoid states that can result in failure, and design an appropriate PM schedule. The proposed method is applied to an ultrasound welding process. A PBN with interventions model was simulated and verified using model checking in PRISM, generating data required to conduct inferential statistical tests to compare the effects of probability of failures between the PBN and PBN with Interventions models. The obtained results demonstrate the validity of the proposed methodology.