Ewald's Conjecture and integer points in algebraic and symplectic toric geometry

We solve several open problems concerning integer points of polytopes arising in symplectic and algebraic geometry. Ewald's Conjecture from 1988 states that if $P$ is a monotone $n$-polytope in $\mathbb{R}^n$ then the set $\mathbb{Z}^n\cap P\cap -P$ contains a unimodular basis of the lattice $\mathbb{Z}^n$. We prove this conjecture for $n$-polytopes which do not recursively contain unimodular triangles. Then we study the combinatorial and asymptotic properties of the function $P \mapsto \mathbb{Z}^n\cap P\cap -P$. Ewald's Conjecture is closely related to problems in toric geometry, and we state the implications of our results in this context. In 2009 Nill proposed a generalization of Ewald's Conjecture which says that if $P$ is an $n$-dimensional lattice smooth polytope in $\mathbb{R}^n$ then $\mathbb{Z}^n\cap P\cap -P$ contains a unimodular basis of $\mathbb{Z}^n$. We prove this conjecture for $n=2$. In the last part of the paper we provide algorithms for the proofs we gave earlier of these conjectures, hence strengthening the interplay between theory and computation in convex geometry/combinatorics, and by extension, in symplectic and algebraic geometry.Comment: 38 pages, 7 figures. Added new result (Corollary 2.12), made minor corrections in the second proof of Theorem 2.6 and the corresponding algorithm, and made a few small changes in Section

Multicultural literature: changes in perceptions and attitudes in fourth graders

In 1954, the Supreme Court voted to end segregation in American public schools. However, this landmark decision did not end racism, discrimination, and inequality. Students of color continue to be invisible across the curriculum. This study is a qualitative teacher action research. The purpose of the study was to assess school personnel perceptions and attitudes toward multicultural education in a rural northern California district, and how the implementation of multicultural literature changes perceptions and attitudes in fourth grade students. The setting for the study took place in Steelhead Elementary, located in a rural section of Northern California. Participants included K-8 educators, bilingual aides, and 60 fourth grade students. Teachers were given a survey, engaged in focus groups, and participated in interviews that measured their general cultural awareness. Students participated in a social justice, critical multicultural literacy curriculum. Major findings include lack of teacher cultural diversity awareness, lack of teacher support for multicultural practices, problematic curriculum, and student consciousness development. This research concludes that critical multicultural literature is essential for addressing racism, discrimination, and lack of cultural representation in the classroom

Improving Stability Prediction in Peripheral Milling of Al7075T6

Chatter is an old enemy to machinists but, even today, is far from being defeated. Current requirements around aerospace components call for stronger and thinner workpieces which are more prone to vibrations. This study presents the stability analysis for a single degree of freedom down-milling operation in a thin-walled workpiece. The stability charts were computed by means of the enhanced multistage homotopy perturbation (EMHP) method, which includes the helix angle but also, most importantly, the runout and cutting speed effects. Our experimental validation shows the importance of this kind of analysis through a comparison with a common analysis without them, especially when machining aluminum alloys. The proposed analysis demands more computation time, since it includes the calculation of cutting forces for each combination of axial depth of cut and spindle speed. This EMHP algorithm is compared with the semi-discretization, Chebyshev collocation, and full-discretization methods in terms of convergence and computation efficiency, and ultimately proves to be the most efficient method among the ones studied.The authors wish to acknowledge the financial support received from HAZITEK program, from the Department of Economic Development and Infrastructures of the Basque Government and from FEDER funds. Additional support was provided by the Tecnologico de Monterrey, through the Research Group in Nanomaterials and Devices Design

Scaling Factor Estimation Using Optimized Mass Change Strategy, Part 2: Experimental Results

The mass change method is used to estimate the scaling factors, the uncertainty is reduced when, for each mode, the frequency shift is maximized and the changes in the mode shapes are minimized, which in turn, depends on the mass change strategy chosen to modify the dynamic behavior of the structure. On the other hand, the aforementioned objectives are difficult to achieve for all modes simultaneously. Thus, a study of the number, magnitude and location of the masses must be performed previously to the modal tests. In this paper, the mass change method was applied to estimate the scaling factors of a steel cantilever beam. The effect of the mass change strategy was experimentally studied by performing several modal tests in which the magnitude, the location and the number of the attached masses were change

Aggregation of under canopy and bare soils in a Mediterranean environment affected by different fire intensities

7 páginas, 4 figuras, 3 tablas.Soil macroaggregation in relation to soil organic matter (SOM) and calcium carbonate(CaCO3) content was studied, before and after experimental fires of different intensities, in two environments (under canopy and on bare soil). In 1995, two experimental fire treatments, based on the addition of different biomass amounts, were applied on a set of nine plots at the Permanent Field Station of La Concordia (Valencia, Spain). Three plots were burned with high intensity fire (T1), three with moderate intensity (T2) and three plots were left unburned to be used as control treatment (T3). Soils under canopy were characterized by higher macroaggregate stability (SMS), SOM content and mean weight diameter of aggregates (MWD) than bare soils, which presented higher CaCO3 contents. After the fires, tendencies to increase were observed in the SOM and SMS of all burned soils, probably because of the incorporation of partially burned plant material. The trends of SMS and SOM in T1 burned soils were towards to decrease with the occurrence of the first erosive rainfalls. These trends continued until the end of the study. MWD of under canopy soils on T1 and of soils on T2 showed a decreasing trend immediately after fire treatments. Not significant differences between sampling periods were found for CaCO3 content, with the exception of under canopy soils on T1 which tended to increase, and showed higher values at the end of the studied period. The differences observed initially between under canopy and bare soil disappeared after one year of fire in T1, which suggests a major degradation of soils affected by this treatment. Significant changes of the studied properties were not observed in unburned soils during one year of research. In these soils, organic matter showed significant correlations with macroaggregate stability and mean weight diameter. However, significant statistical relationships were not observed between the Studied properties in burned soils, showing that fire impact probably affected other soil characteristics related to soil aggregation.We thank the financial support from the Agreement Generalitat Valenciana — CSIC (2005020112) “Impacto de los incendios forestalesrepetidos sobre los procesos de erosión hídrica del suelo y la recuperación de la cubierta vegetal. Seguimiento y evaluación en una estación permanente de campo”, and the Ministerio de Educación y Ciencia of the Spanish Government project “Procesos y balances hidrológicos y de sedimentos a diferentes escalas espaciales en ambientes mediterráneos: Efectos de la variabilidad climática y los cambios de uso del suelo” (PROBASE CGL2006-11619).Peer reviewe

Evolution of web positioning factors and adaptation of optimization tools

Las herramientas de optimización web, Search Engine Optimization (SEO), se utilizan para analizar y mejorar los sitios web en relación a distintos factores de posicionamiento. Esta investigación estudia la evolución de las estrate- gias de posicionamiento web y analiza la adaptación de las herramientas de optimización a estos factores. Además, se estudian qué factores de posicionamiento están presentes en las herramientas SEO más populares. En la fase experimen- tal se analiza el grado en que las estrategias de optimización mejoran el posicionamiento, y en qué medida se encuentran esas funcionalidades en las herramientas SEO. Adicionalmente se han analizado foros y blogs oficiales para descubrir nuevas pautas de evolución de los motores de búsqueda y el grado en que las herramientas SEO pueden adaptarse a dichos cambios. Aunque estas herramientas optimizan el posicionamiento, los resultados sugieren la necesidad de intro- ducir importantes mejoras que aumenten su potencialidad futura.Search Engine Optimization (SEO) tools are designed to analyze and optimize resources regarding positioning factors. Web positioning techniques are applied in order to improve the relevancy of web resources. Webmasters usually use SEO tools to analyze a web site according to some positioning factor. They are required to be updated to achieve two basic goals: to increase the user’s satisfaction while searching the web and to decrease web spamming. We have studied the trends that affect positioning algorithms and optimization techniques. Several SEO tools were analysed in order to learn which functionalities have been implemented. Furthermore, an experiment was performed to test how the positioning factors help optimize the results and if these factors are present in the functionalities found in the SEO tools. Finally, a literature review was carried out to detect future trends in search engines’ algorithms. Results show that SEO tools help in the optimization process but to an insufficient degree; therefore the algorithm’s evolution study suggests that there is a need for major updates in the short ter

Hydrological properties of a Mediterranean soil burned with different fire intensities

8 páginas, 5 figuras, 3 tablas.The influence of vegetation cover on soil hydrological properties and its response to the impact of different fire intensities, in a Mediterranean forest environment, has been evaluated. The study was carried out in the Permanent Experimental Field Station of La Concordia (Lliria-Valencia, Spain), on a set of nine erosion plots (4 x 20 m(2)). The Station is located on a calcareous hillside S-SE oriented, with soils of Rendzic Leptosol type and supporting Mediterranean shrubland vegetation. All runoff generated and sediment produced in every rain event was collected from each plot. The set up includes a system of sensors for the continuous monitoring of climatic parameters (air temperature and humidity, rain volume, intensity, etc.). In June 1995, a set of experimental fires was carried out to the Station. Three of the plots were burned with high intensity fire, three with moderate intensity and the remaining were left unaltered. Soil water content and water retention capacity (WRC) were measured in the different plots and in two different vegetation covers: under canopy (UC) and in bare soil (BS). The pF curves were also obtained for each fire treatment. A year after the fires (June 1995-June 1996), great differences, reaching 77.15%, in runoff generation between fire treatments and the control plots were observed. No significant differences were detected on water retention capacity between soils UC and BS in the burned plots. However, these differences appeared in the control plots, giving UC and BS values of 13% and 18%, respectively. Plots corresponding to the high intensity fire treatment showed values of WRC significantly higher than those of the moderate intensity and of the control treatments. The pF curves show that the values of water volume, at the different pressure points studied, were slightly greater on UC soil. Values obtained for BS samples are higher in the fire treatments, showing significant differences in respect to the control plots at pF 1 and 2. These differences were also observed for UC soil, but in this case at pF 2, 2.5 and 4.2.This work has been supported by the European Union (QLRT-2000-00289), the Spanish Ministry of Science and Technology (CICYT) REN2001-1716 and Convenio (Agreement) Generalitat Valenciana – CSIC (02020024).Peer reviewe

La investigación cualitativa a través del estudio de casos: referencia a la investigación en turismo

Investigamos para analizar y explicar fenómenos, pero no siempre podemos llevar a cabo las investigaciones mediante el empleo de metodologías basadas en el planteamiento y contraste de hipótesis sobre la base de un marco teórico existente, validado y vigente. En este trabajo trataremos de justificar la utilización de la metodología cualitativa como estrategia de investigación en el área de organización de empresas. Así analizamos los fundamentos, utilidades y limitaciones del estudio de casos, para posteriormente, sugerir, apoyándonos en la literatura consultada, las etapas que debe abordar una investigación con casos de calidad. Finalmente, y con el fin de justificar la relevancia que dicha metodología esta tomando en los últimos años en investigaciones relacionadas con el sector turístico, analizamos la presencia de la misma en los trabajos publicados en las revistas de mayor impacto de la materia.We research to analyze and explain phenomena, but we can not always carry out scientific studies using hypothesis testing methodologies based on an existing, validated and in used theoretical framework. In this paper we try to justify the use of qualitative techniques as a research strategy in the business administration area. The rationale, usefulness and limitations of case study methodology are scrutinized, in order to suggest, based on the existing literature, the stages that a quality cases research should follow. Finally, in order to justify the relevance that this methodology is taking in recent years in the field of tourism, we detail its use in the higher impact journals

Drilling Process in γ-TiAl Intermetallic Alloys

Gamma titanium aluminides (gamma-TiAl) present an excellent behavior under high temperature conditions, being a feasible alternative to nickel-based superalloy components in the aeroengine sector. However, considered as a difficult to cut material, process cutting parameters require special study to guarantee component quality. In this work, a developed drilling mechanistic model is a useful tool in order to predict drilling force (Fz) and torque (Tc) for optimal drilling conditions. The model is a helping tool to select operational parameters for the material to cut by providing the programmer predicted drilling forces (Fz) and torque (Tc) values. This will allow the avoidance of operational parameters that will cause excessively high force and torque values that could damage quality. The model is validated for three types of Gamma-TiAl alloys. Integral hard metal end-drilling tools and different cutting parameters (feeds and cutting speeds) are tested for three different sized holes for each alloy.RTC-2014-1861-4, INNPACTO DESAFIO II. Spanish Governmen

Ferrocene-Decorated Phenol Derivatives by Trapping ortho-Quinone Methide Intermediates with Ferrocene

The InCl3-catalyzed reaction of ferrocene with ortho-hydroxybenzyl alcohols is reported and represents a convenient route for the synthesis of ferrocenyl phenols. This carbon–carbon bond forming process is believed to proceed through an ortho-quinone methide intermediate that can be intercepted by ferrocene through a Friedel–Crafts-type process. Preliminary cytotoxic screening carried out on several cancer cell lines revealed that some of the compounds exhibit moderate cytotoxicity