Differential growth of wrinkled biofilms

Biofilms are antibiotic-resistant bacterial aggregates that grow on moist surfaces and can trigger hospital-acquired infections. They provide a classical example in biology where the dynamics of cellular communities may be observed and studied. Gene expression regulates cell division and differentiation, which affect the biofilm architecture. Mechanical and chemical processes shape the resulting structure. We gain insight into the interplay between cellular and mechanical processes during biofilm development on air-agar interfaces by means of a hybrid model. Cellular behavior is governed by stochastic rules informed by a cascade of concentration fields for nutrients, waste and autoinducers. Cellular differentiation and death alter the structure and the mechanical properties of the biofilm, which is deformed according to Foppl-Von Karman equations informed by cellular processes and the interaction with the substratum. Stiffness gradients due to growth and swelling produce wrinkle branching. We are able to reproduce wrinkled structures often formed by biofilms on air-agar interfaces, as well as spatial distributions of differentiated cells commonly observed with B. subtilis.Comment: 19 pages, 13 figure

The Economic Value of Basin Protection to Improve the Quality and Reliability of Potable Water Supply: Some Evidence from Ecuador

This study estimates the willingness to pay (WTP) of Loja’s households to protect two micro-basins that supply over 40 percent of potable water to the city. Results indicate that households have an average WTP of $5.80 per month, which corresponds to a 25 percent increase in the self-reported monthly water bill, to preserve the basins.Basin protection, contingent valuation, Loja, Ecuador, Environmental Economics and Policy, Land Economics/Use,

Biodiesel Mandate Laws in Argentina and Brazil: An Estimation of Soybean Oil Foregone Export Revenues

Replaced with revised version of paper 02/22/08.Research and Development/Tech Change/Emerging Technologies,

Searching for molecular outflows in Hyper-Luminous Infrared Galaxies

We present constraints on the molecular outflows in a sample of five Hyper-Luminous Infrared Galaxies using Herschel observations of the OH doublet at 119 {\mu}m. We have detected the OH doublet in three cases: one purely in emission and two purely in absorption. The observed emission profile has a significant blueshifted wing suggesting the possibility of tracing an outflow. Out of the two absorption profiles, one seems to be consistent with the systemic velocity while the other clearly indicates the presence of a molecular outflow whose maximum velocity is about ~1500 km/s. Our analysis shows that this system is in general agreement with previous results on Ultra-luminous Infrared Galaxies and QSOs, whose outflow velocities do not seem to correlate with stellar masses or starburst luminosities (star formation rates). Instead the galaxy outflow likely arises from an embedded AGN.Comment: Accepted for publication in MNRAS. 13 pages, 11 figures, 4 table

Use of resistivity measurements to detect urban caves in Mexico City and to assess the related hazard

International audienceIn the XIX century when Mexico City was much smaller than at present, there was non-regulated mining of building materials in a region of tuffs northwest of the city in an inhabited countryside. With the growth of the city during the XX century, this region was increasingly populated and in the 1970's many two-level bricks houses were built, without regard for underground caves created by the earlier extractions. Some ground sinkings in adjacent areas alarmed the residents who now are worried about this permanent hazard. An association of residents contracted a private company for a geophysical study in order to know the distribution of the caves. Resistivity measurements were taken in the area to detect the caves in order to alert city authorities. Resistivity data along most of the streets were collected with the array pole-dipole that consisted of three grounded electrodes. We performed 2-D dimensional inversions to the data in order to get a 2-D resistivity image of every street. This is similar to a resistivity cross-section of the ground but obtained from the inversion of pole-dipole and Schlumberger resistivity data simultaneously. Using the information of previous drills we modified our programming code in order to perform constrained inversion and to get more accurate resistivity models in agreement with the drills. From the resistivity models obtained for every street it was possible to produce a map which shows the horizontal distribution of the resistive bodies at a depth of 12m. These resistive bodies show coherent alignments that seem to correspond with a distributions of interconnected caves or tunnels used for extracting the sandy-tuffs. From these kind of interpretation method it was intended to get a more accurate horizontal distribution of the excavated areas in order to better know the urbanized area affected and lead the authorities to remedy the area with refill material

Technological research methodology to manage organizational change

Change is a process that is part of the nature of people; however, within organizations, it should be seen as an invention that will generate benefits in the markets. The main objective of this work is to design a technological methodology to manage change from seven administrative models. For this, a bibliographic review was carried out; the method applied was analysis-synthesis; the example technique was used to comment; the support instruments were a standard data collection form and a comparative table to analyze this data vertically and horizontally. The methodology was validated in the research units of a local university. The main results were 1) The change of management within organizations is an invention; 2) administrative models of change are used to manage it; 3) but, to be successful in managing change, the methodology of technological research is required in addition to the administrative process

FATTY ACIDS CONTENT IN UNGURAHUA OIL (OENOCARPUS BATAUA) FROM ECUADOR. FINDINGS ON ADULTERATION OF UNGURAHUA OIL IN ECUADOR

 Objective: The aim of this study was to determine the fatty acids composition in an ungurahua seeds oil (Oenocarpus bataua) sample cultivated in Ecuador and to determine eventual adulteration in the composition of commercial ungurahua oil.Methods: Oil was obtained from ungurahua seeds using the cold pressing method. Fatty acids analysis was performed using the gas chromatography (GC) method with a mass selective detector and using the database library NIST14.L to identify the compounds.Results: Methyl esters fatty acids were identified from ungurahua (O. bataua) using the GC mass spectrometer analytical method. Ungurahua oil presented a high content of monounsaturated fatty acids with 82.03% of oleic acids. A fraud in the composition of fatty acids present in commercial ungurahua oil was found as fatty acids had a value of only 36.77% of oleic acids. The content of linoleic acid can be used to determine adulteration of this oil.Conclusions: Ungurahua seeds are a good source of monounsaturated and fatty acids. The content of oleic acid is higher than in olive oil. Ungurahua can help reducing cardiovascular diseases risk in Ecuador due to its good composition of monounsaturated fatty acids. Ungurahua oil is a good option to be used in the food industry for different uses

FATTY ACIDS COMPOSITION IN MACADAMIA SEDES OIL (MACADAMIA INTEGRIFOLIA) FROM ECUADOR

Objective: The aim of this study was to determine the fatty acids composition in a macadamia seeds oil sample cultivated in Ecuador.Materials & Methods: macadamia oil was obtained of macadamia seeds using the cold pressing method. Fatty acids analysis was carried out using the Gas Chromathography method with a Mass Selective Detector (GC/MSD) and using the data base Library NIST14.L to identify the compounds.Results: macadamia seeds have a high content of unsaturated fatty acids with 41.36% of oleic acid. Macadamia seeds oil has 37.77% of polyunsaturated fatty acids of which 3.79% ɷ6 α- Linoleic and 33.98% of ɷ3 α- Linolenic. Macadamia seeds only have 9.33% of palmitic acid. Conclusions: Macadamia seeds are a good source of monounsaturated fatty acids oleic acid and with a good content of ɷ6 α- Linoleic and ɷ3 α- Linolenic. This profile enables their use as a good and healthy oil to be used in the food industry in Ecuador. Keywords: Macadamia, Macadamia integrifolia, Fatty acids, Gas chromatography-mass selective detector, Methyl ester, Omega acids

Edge dislocations in crystal structures considered as traveling waves of discrete models

The static stress needed to depin a 2D edge dislocation, the lower dynamic stress needed to keep it moving, its velocity and displacement vector profile are calculated from first principles. We use a simplified discrete model whose far field distortion tensor decays algebraically with distance as in the usual elasticity. An analytical description of dislocation depinning in the strongly overdamped case (including the effect of fluctuations) is also given. A set of $N$ parallel edge dislocations whose centers are far from each other can depin a given one provided $N=O(L)$, where $L$ is the average inter-dislocation distance divided by the Burgers vector of a single dislocation. Then a limiting dislocation density can be defined and calculated in simple cases.Comment: 10 pages, 3 eps figures, Revtex 4. Final version, corrected minor error