Bias in density estimations using strip transects in dry open-country environments in the Canary Islands

We studied bias in density estimations derived from strip transects in dry open-country in the Canary Islands. We also present some critical remarks on García-del-Rey’s (2005) paper regarding strip transects and the validity of comparisons based on population densities of birds in scrublands on Tenerife island using two different methods: territory mapping and strip transect sampling. Although strip transects with census belts of 25 m do not account for detectability, this method only slightly undervalues true density estimates, and allowed to detect more than 85% of birds present in poorly vegetated environments in the Canary Islands. Previously published works on distribution and abundance of terrestrial birds in the Canary Islands using the strip transect sampling with belts of 25 m on both sides of the observer, thus provide reliable information that only slightly underestimates true densities

Descubriendo Patrones Craneofaciales Usando Datos Cefalométricos Multivariados para la Toma de Decisiones en Ortodoncia

Indexación: Web of Science; Scielo.The aim was to find craniofacial morphology patterns in a multivariate cephalometric database using a clustering technique. Cephalometric analysis was performed in a sample of 100 teleradiographs collected from Chilean orthodontic patients. Thirty cephalometric measurements were taken from commonly used analysis. The computed variables were used to perform a clustering analysis with the k-means algorithm to identify patterns of craniofacial morphology. The J48 decision tree was used to analyze each cluster, and the ANOVA test to determine the statistical differences between the clusters. Four clusters were found that had significant differences (P<0.001) in 24 of the 30 variables studied, suggesting that they represent different patterns of craniofacial form. Using the decision tree, 8 of the 30 variables appeared to be relevant for describing the clusters. The clustering analysis is effective in identifying different craniofacial patterns based on a multivariate database. The distinct clusters appear to be caused by differences in the compensation process of the facial structure responding to a genetically determined cranial and mandible form. The proposed method can be applied to several databases, creating specific classifications for each one of them. KEY WORDS: Craniofacial patterns; Morphological patterns; Clustering technique; Orthodontics.RESUMEN: El objetivo fue encontrar patrones morfológicos craneofaciales, a partir de una base de datos cefalométricos multivariada, utilizando una técnica de clustering. Se realizó un análisis cefalométrico a una muestra de 100 telerradiografías pertenecientes a pacientes chilenos de ortodoncia. Treinta medidas cefalométricas obtenidas de los análisis más utilizados fueron registradas. Las variables computadas se utilizaron para realizar un análisis de clustering con el algoritmo k-medias, para identificar patrones de morfología craneofacial. El árbol de decisión J48 se utilizó para analizar cada cluster, y test de ANOVA para determinar diferencias estadísticamente significativas entre los clusters. Se encontraron cuatro clusters con diferencia estadísticamente significativas (p<0,001) en 24 de las 30 variables estudiadas, lo que sugiere que efectivamente corresponden a diferentes patrones craneofaciales. Utilizando el árbol de decisión, se pudo determinar que 8 de las 30 variables resultaron ser relevantes en la definición de los clusters. El análisis de clustering es efectivo en identificar patrones morfológicos craneofaciales usando una base de datos multivariada. Los distintos cluster encontrados, aparentemente se formarían a partir de diferencias en el proceso de compensación de la estructura facial, en respuesta a la forma mandibular genéticamente determinada. El método propuesto puede ser aplicado a múltiples bases de datos, creando clasificaciones específicas para cada una de ellas. PALABRAS CLAVE: Patrones craneofaciales; Patrones morfológicos; Técnica de clustering; Ortodoncia.http://ref.scielo.org/qdkkz

NEUTRONIC AND CFD-THERMAL HYDRAULIC ANALYSES OF VERY-SMALL, LONG-LIFE, MODULAR (VSLLIM) REACTOR

Neutronic and CFD-thermal hydraulic analyses are performed of the Very-Small, Long-LIfe, and Modular (VSLLIM) nuclear reactor. This reactor was developed at the University of New Mexico’s Institute for Space and Nuclear Power Studies (UNM-ISNPS) to generate 1.0 – 10 MWth for extended periods without refueling. It offers passive operation and safety features and redundant control and would be fabricated, assembled and sealed in the factory. During nominal operation and after shutdown, the VSLLIM is cooled by natural circulation of in-vessel liquid sodium, with the aid of an in-vessel chimney and annular helically-coiled tubes Na-Na heat exchanger (HEX) in the downcomer. In case of a malfunction of the Na-Na HEX, the reactor shuts down, and the decay heat generated in the core is removed by natural circulation of the in-vessel liquid sodium with the aid of redundant passive means. These include variable-conductance liquid-metal heat pipes that are embedded in the upper part of the reactor primary vessel wall, and natural circulation of ambient air along the outer surface of the reactor guard vessel wall. The VSLLIM reactor core is loaded with hexagonal assemblies of 19 UN fuel rods clad in HT-9 steel and with scalloped BeO walls, clad also in HT-9 steel. In addition to helping achieve an almost uniform flow distribution in the fuel assemblies, the scalloped BeO walls, together with the BeO axial and radial reflectors, increase the hot-clean reactivity for achieving long full-power operation life, at a relatively low UN fuel enrichment. During nominal operation, the inlet and exit coolant temperatures in the reactor core are maintained at 610 K, and \u3c 820 K to minimize embrittlement and corrosion of the HT-9 steel cladding, core structure, and reactor vessel by liquid sodium. This research conducted neutronic and thermal-hydraulics analyses to investigate and quantify the passive operation and safety features of the Very-Small, Long-LIfe, and Modular (VSLLIM). The research tasks carried out include: (a) Performing neutronic analyses of the VSLLIM to investigate the effects of several design and material choices on the cold and hot-clean reactivity, for achieving long operation life without refueling. Also calculate the cold-clean reactivity shutdown margins of the emergency shutdown system (ESS) and reactor control (RC), and the beginning of life (BOL) hot-clean reactivity. Investigated are the effect of UN fuel enrichment, and the material of the axial and radial reflectors. These analyses calculated the neutron energy spectrums and the radial and axial fission power distributions. These are in addition to determining the temperature reactivity feedback effects due to the UN fuel, sodium coolant, HT-9 steel cladding and core structure, BeO in the driver core and axial radial reflectors, and the Doppler broadening of neutron cross-sections. To estimate the full-power operation lives of the VSLLIM reactor at different thermal powers, fuel depletion calculations are carried out at hot-clean operation condition. (b) Performing thermal-hydraulic and computational fluid dynamics (CFD) analyses during nominal reactor operation and after shutdown. These analyses estimated the friction number for the liquid sodium flow in the core hexagonal UN fuel assemblies, with scalloped wall as a function of the flow Reynolds number. The flow and temperature distributions in the UN fuel assemblies are calculated, at different reactor thermal powers and inlet and exit core temperatures of 610 K and \u3c 820 K, respectively. (c) Performing CFD analyses to quantify the passive decay heat removal by natural circulation of ambient air along the outer surface of the reactor guard vessel. Both, after reactor shutdown and in the case of a malfunction of the in-vessel Na-Na HEX. The performed neutronics and fissile depletion analyses of the VSLLIM confirmed that a UN fuel enrichment of 13.76% is sufficient for achieving high enough hot-clean excess reactivity for operating VSLLIM reactor without refueling for ~92 and 5.8 full power years (FPY) at 1.0 and 10 MWth, respectively. Results confirmed sufficient cold-clean reactivity shutdown margins using either the reactor control (RC) or the emergency shutdown system (ESS), independently. In addition to having two independent reactor shutdown systems, results show that the negative temperature reactivity feedback is capable of shutting down the reactor with a modest increase in the temperatures of the UN fuel and the in-vessel liquid sodium. Results also show that the neutron energy spectrum in the VSLLIM reactor core is hard, which reduces the inventory of minor actinides in UN fuel during reactor operation. Because of its low operating temperatures, \u3c 812 K at 10 MWth and UN fuel low average power density (\u3c 23.47 MWth/m3), the fuel in the VSLLIM core experiences practically no swelling and retains practically all fission gas release. The performed CFD-thermal-hydraulics analyses investigated the effects of using metal fins along the outer surface of the guard vessel wall and changing the width of the cold air intake duct on the decay heat removal rate and the time after shutdown for cooling the in-vessel liquid sodium to 400 K. Results show that without metal fins, the heat removal rate of the decay heat is 244 kWth immediately after shutdown. However, within 8 minutes after shutdown, natural circulation of ambient air along the outer surface of the guard vessel removes more heat than is being generated by radioactive decay in the core. Consequently, the average in-vessel sodium temperature drops from 682 K to 400 K, within 120 hrs after shutdown. Using metal fins along the outer surface of the guard vessel increases the total area for heat transfer and the decay heat removal rate by 13.5%, reducing the time for the average temperature of the in-vessel liquid sodium to decrease to 400K in ~100 hrs. Without metal fins, reducing the width of the cold air intake duct by 50% decreases the decay heat removal rate by 35%, increasing to ~ 346 hrs the cooling time of the in-vessel sodium to 400 K. These results demonstrate that the decay heat removal by natural circulation of ambient air from the outer surface of the reactor guard vessel wall, with and without metal fins, is quite effective. Additionally, the results show that the temperature of the in-vessel sodium after shutdown remain safely, ~470 K below its boiling point (~1156 K at 0.1 MPa). The performed CFD analyses investigated the friction factor for laminar, transition, and turbulent flows in hexagonal bundles of bare tube and also investigated with flat and scalloped walls. The results for the bundles with flat walls are in good agreement with previously reported experimental data by others. The CFD results and the reported experimental data for bundles with flat walls and various numbers of tubes, (7, 19, 37, and 61), in a triangular lattice with 1.07 \u3c P/D \u3c 2.416, are used to develop a continuous correlation of the friction factor as a function of P/D and Rein. The developed correlation, for P/D up to 3.0, and a wide range of tubes in the bundles (N = 7 – 331), spans all three flow regions (102 \u3c Rein \u3c 106) and is in excellent agreement with the compiled numerical and experimental database. The results also validated the applicability of the developed friction factor correlation to the VSLLIM reactor hexagonal bundles with scalloped walls. The developed continuous friction factor correlation is within 5% - 8% of the CFD data generated for the scalloped walls bundles with 19 and 37 rods or tubes. Results also showed that scalloped walls reduce the bypass flow next to the wall, while increasing the flow in the interior subchannels in the bundles, thus improving heat transfer. Higher flow in interior subchannels enhances the thermal-hydraulics in the VSLLIM reactor core and reduces the maximum temperature at a given Rein

The role of magnetoplasmons in Casimir force calculations

In this paper we review the role of magneto plasmon polaritons in the Casimir force calculations. By applying an external constant magnetic field a strong optical anisotropy is induced on two parallel slabs reducing the reflectivity and thus the Casimir force. As the external magnetic field increases, the Casimir force decreases. Thus, with an an external magnetic field the Casimir force can be controlled.The calculations are done in the Voigt configuration where the magnetic field is parallel to the slabs. In this configuration the reflection coefficients for TE and TM modes do not show mode conversion.Comment: contribution to QFEXT09, Norman, Oklahoma 200

Development of the instrumentation of the botafoc breakwater nº 8 caisson

Balearic Port Authority has developed an instrumentation system for the #8 caisson of the Botafoc breakwater that integrates 12 pressure sensors located at three surfaces, two in contact with the sea water and another with the bottom. This design was completed with an inertial system that measures the angular velocities and the accelerations over the three Cartesian axes. Consequently, the system measures actions (pressures) and reactions (movements and accelerations) experimented by the caisson, due to sea waves and/or other service loads. R+D department of the Port Authority and Polytechnic University of Madrid are working on two directions, the development of new theories on vertical breakwater design that go beyond Goda and Sainflou, and on the creation of a real-time critical structure alarm system, based on the instrumentation installed. This alarm system has two main parts: the instrumentation itself that collects data and processes it on real-time (the data processing compares the pressure law suffered by the caisson in every step process with the design critical state of the caisson, in this case the Goda pressure law for a 6.5 m wave), giving a security coefficient that points out the risk level on real-time; and the alarm system consisting of a monitoring panel located in the Port Control Center that shows the risk level and advises in case of an incidental evacuation of this critical portuary installation

Variación geográfica de la riqueza de especies invernantes en la península Ibérica. Estacionalidad y determinismo ambiental.

Peer Reviewe

Pull-in control due to Casimir forces using external magnetic fields

We present a theoretical calculation of the pull-in control in capacitive micro switches actuated by Casimir forces, using external magnetic fields. The external magnetic fields induces an optical anisotropy due to the excitation of magneto plasmons, that reduces the Casimir force. The calculations are performed in the Voigt configuration, and the results show that as the magnetic field increases the system becomes more stable. The detachment length for a cantilever is also calculated for a cantilever, showing that it increases with increasing magnetic field. At the pull-in separation, the stiffness of the system decreases with increasing magnetic field.Comment: accepted for publication in App. Phys. Let

Analysis of Indoor Radon Distribution Within a Room By Means of Computational Fluid Dynamics (CFD) Simulation

Radon gas is recognized by international organizations such as the United States Environmental Protection Agency (US-EPA) as the main contributor of radiation environmental to which human beings are exposed. Therefore, the evaluation of indoor radon concentration is a matter of public interest. The emanation and the income of the gas inside a room will generate a negative impact on the quality of the air when the place is not properly ventilated. Understanding how this gas will be distributed inside the room will allow to predict the spatial and temporal variations of radon levels and identify these parameters will provide important information that researchers can be used for calculate radiation dose exposure. Consequently, this studies can prevent a health risk for the people that live or work within the room. Currently, several researchers use the technique called Computational Fluid Dynamics (CFD) to simulate the distribution of gas radon, making use of the various commercial programs that exist in the market. In this work, three simulations were developed in rooms that have a similar geometry but different dimensions, in order to observe how the gas is distributed inside a closed space and to analyze how this distribution varies when the volume of the place is increased. The results show that as the volume of the site increases the radon is mitigated more rapidly and therefore has lower levels of concentration of this gas, as long as the level of radon emanation is kept constant

Preferencias de hábitat, densidad y diversidad de las comunidades de aves en Tenerife (Islas Canarias)

Bird distribution and abundance are described and analyzed in Teneriffe (Canary Islands). Inter–habitat differences in density, diversity and species richness are shown in table 1. Figure 2 shows the main determinants of bird species richness in Teneriffe, and tables 2 and 3 and figure 3 show the species–specific patterns of spatial variation abundance (more detailed for Anthus berthelotii, Fringilla coelebs canariensis, Fringilla teydea, Parus caeruleus teneriffae, Phylloscopus canariensis, Regulus teneriffae, Serinus canarius and Turdus merula cabrerae). Deeply transformed environments due to human impact (urban habitats, agricultural mosaics, banana plantations) have high bird densities and species richness, even higher than those measured in native, unmodified habitats such as laurel forests or mature pinewoods. Urban environments in Teneriffe are very permeable to native bird fauna, as they have been occupied by many widespread endemic species/subspecies. Many of the endemic, well defined species or subspecies of island birds have high population densities within native, untransformed habitats. Density compensation and niche expansion is not a common phenomenon in the avifauna of Teneriffe. Nevertheless, all species/subspecies broadening the inter–habitat or altitudinal distribution are endemic of the Canary Islands.Mediante el empleo de transectos lineales, se describen las preferencias de hábitat, la distribución altitudinal y la abundancia de la avifauna reproductora de Tenerife (Islas Canarias). Los hábitats profundamente transformados debido a la acción humana (e.g., áreas urbanas, mosaicos agrícolas, plantaciones de plátanos) tienen elevadas densidades y riquezas de especies, que llegan a ser tan altas o mayores que las observadas en medios autóctonos no transformados como laurisilvas y pinares maduros. Muchas especies/subespecies taxonómicamente bien diferenciadas de las poblaciones continentales están distribuidas mayoritaria o exclusivamente en hábitats autóctonos poco degradados. Las hipótesis de la compensación de densidades y la expansión de nicho en poblaciones insulares no parecen cumplirse de modo generalizado en Tenerife. No obstante, todas las especies o subespecies que muestran una mayor amplitud de distribución en Tenerife son endémicas del archipiélago canario

Luminescent and Scintillating Properties of Lanthanum Fluoride Nanocrystals in Response to Gamma/Neutron Irradiation: Codoping with Ce Activator, Yb Wavelength Shifter, and Gd Neutron Captor

A novel concept for detection and spectroscopy of gamma rays, and detection of thermal neutrons based on codoped lanthanum fluoride nanocrystals containing gadolinium is presented.The trends of colloidal synthesis of the mentioned material, LaF3 co-doped with Ce as the activator, Yb as the wavelength-shifter and Gd as the neutron captor, is reported. Nanocrystals of the mentioned material were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), optical absorption, and photoluminescence spectroscopy. Gamma detection and its potential spectroscopy feature have been confirmed. The neutron detection capability has been confirmed by experiments performed using a 252Cf neutron source.Comment: 5 figures, 16 page