Beyond Alpha: Lower Bounds for the Reliability of Tests

The most common lower bound to the reliability of a test is Cronbach’s alpha. However, several lower bounds exist that are definitely better, that is, higher than alpha. An overview is given as well as an algorithm to find the best: the greatest lower bound

An Unbiased Estimator Of The Greatest Lower Bound

The greatest lower bound to the reliability of a test, based on a single administration, is the Greatest Lower Bound (GLB). However the estimate is seriously biased. An algorithm is described that corrects this bias

Small is beautiful... or not?

Intervention au 34e congrès LIBER qui s\u27est tenu à Groningue aux Pays-Pas du 6 au 9 juillet 2005

Exploring the UV spectral range to constrain the evolution of massive galaxies in varying environments and varying redshift

Las galaxias más masivas del Universo local son las galaxias de tipo temprano (del inglés, ETGs) que comprenden las galaxias elípticas y lenticulares. El grueso de sus poblaciones de estrellas son viejas y prácticamente no están formando nuevas estrellas. Su actividad de formación estelar no es lo que llegó a ser en las etapas tempranas del Universo, donde grandes cantidades de gas se transformaron en estrellas. La formación de estrellas se detuvo rápidamente y las ETGs evolucionaron como sistemas rojos y viejos. Cuáles fueron los mecanismos físicos responsables de detener la creación de nuevas estrellas sigue siendo un misterio, aunque se cree que las contribuciones de los núcleos activos de galaxias (del inglés, AGNs) pudieron transformar estos sistemas estelares en objetos evolucionando pasivamente con escasa formación estelar. Las estrellas viejas de las ETGs emiten la mayor parte de su luz en el rango espectral óptico. El óptico, sin embargo, es relativamente insensible a pequeñas fracciones de poblaciones estelares jóvenes, cuya luz domina en el rango ultravioleta (UV). Afortunadamente, el UV es un trazador óptimo de las poblaciones estelares más calientes como las estrellas jóvenes. Estudios fotométricos en el UV han puesto de manifiesto que las ETGs pueden tener formación de estrellas a un ritmo muy bajo. Sin embargo, el rango UV en los espectros de las ETGs no ha sido explorado para determinar sus poblaciones jóvenes. El objetivo de esta tesis es cuantificar estas poblaciones estelares jóvenes de las ETGs masivas usando las líneas de absorción de sus espectros. Hemos usado nuevos modelos de poblaciones estelares para analizar, por primera vez, índices espectrales ópticos y del UV cercano simultáneamente. Comparamos las observaciones con las predicciones de los modelos de dos parametrizaciones de las historias de formación estelar (del inglés, SFH) de las galaxias masivas. Primero hemos investigado si la formación de estrellas residual es una característica común entre la población de ETGs, mediante la suma de miles de espectros de galaxias masivas a un desplazamiento al rojo medio de z~0.4. De estos espectros sumados hemos podido obtener las fracciones de población joven en función de la masa de la galaxia. Hemos encontrado que las ETGs masivas tienen en promedio una fracción de estrellas jóvenes formadas en los últimos 2 mil millones de años por debajo del 1%, y que ésta fracción es mayor para las galaxias menos masivas. Esta tendencia con la masa es consistente con el hecho que las galaxias menos masivas tienen SFH más extendidas en el tiempo que las más masivas. También hemos visto que las galaxias masivas sintéticas de las simulaciones cosmológicas producen demasiadas estrellas de edades intermedias. Esto implica que los procesos para suprimir la formación de estrellas en galaxias masivas y mantenerla suprimida en el tiempo, aun necesitan ser comprendidos. Nuestros resultados ponen rigurosos límites que necesitan ser satisfechos por las simulaciones. Para intentar entender el origen de estas poblaciones jóvenes, hemos analizado espectros resueltos espacialmente para obtener información de dónde están situadas en las galaxias. Para ello, hemos analizado un tipo especial de ETGs: las galaxias más brillantes de los cúmulos de galaxias (del inglés, BCGs). Estas galaxias se encuentran en el centro de los potenciales gravitatorios de los cúmulos de galaxias. Nuestro estudio de 6 BCGs cercanas ha demostrado que sus estrellas jóvenes están en el interior de <2 kpc del centro de las galaxias, es decir, en los núcleos. Las pequeñas fracciones de estrellas jóvenes que encontramos son consistentes con un origen in-situ, es decir, la formación de estrellas residual puede producirse gracias al material reciclado de la muerte de estrellas de generaciones anteriores o del gas inicial residual. Sin embargo, debido a la ubicación de estos objetos, un origen ex-situ a través los efectos y procesos del entorno del no puede ser descartado. Estudiar las componentes estelares jóvenes en galaxias reliquias nos ayuda a entender los orígenes de la formación estelar reciente que detectamos en las galaxias ETGs normales. Estas galaxias reliquias, masivas y compactas, han sobrevivido intactas desde su formación a alto desplazamiento al rojo hasta el Universo local, es decir, sin haber experimentado un crecimiento tanto en tamaño como en masa a través de fusiones e interacciones con otras galaxias. Por ello, hemos estudiado la contribución de las poblaciones jóvenes en la región central de 1 kpc de la galaxia NGC 1277, la galaxia reliquia por excelencia del Universo cercano. Encontramos una población joven que contribuye menos del 1%, similar a los resultados previos, lo que apunta a que la formación estelar reciente encontrada en galaxias masivas ETGs puede estar relacionada con los procesos intrínsecos de las galaxias.Early-type galaxies (ETGs), consisting of ellipticals and lenticulars, are the most massive galaxies in the local Universe. The bulk of their stellar populations are characterised as being old with negligible recent star formation activity, having followed a passive evolution from the high-redshift Universe to the present day. Their star formation activity is not what used to be at the early Universe (z > 2), where large amounts of gas were transformed into stars. Star formation was virtually extinguished in rather short time and ETGs evolved as red and dead objects. The exact physical mechanisms responsible for quenching the star formation in these massive systems at high-redshift is not completely resolved. Although, it is widely considered that AGN feedback could turn these stellar systems into passively evolving objects without significant formation of new stars. There is growing observational and theoretical evidences for a two-phase formation scenario for ETGs. According to this picture, during the first phase the cores of present-day ETGs are formed at z > 2 dissipatively, while in the second phase the outer regions are a result of mergers and accretion. This is supported by a large number of studies that have shown that massive galaxies at z > 2 are more compact than their local counterparts, and have experienced significant growth both in size and, to a lesser degree, in mass. This suggests that these high-z massive compacts are the cores of local ETGs formed at high redshift, while the outer regions are where the accreted material due to dissipationless mergers (i.e. gas-poor) is deposited. This second phase is mostly ”dry”, i.e. does not trigger star formation, at least not in any efficient way. The bulk of the stars in ETGs are ancient and emit much of their light in the optical spectral range. However, the optical is relatively insensitive to small fractions of young stellar populations, whose light dominate the ultraviolet (UV). Studies of the optical range are therefore, biased to the old stellar populations. Fortunately, the UV is an optimal tracer of the hottest stellar populations such as young stars. Photometric studies in the UV have previously suggested that ETGs might have recent low-level star formation. However, the UV window of ETG’s spectra has not been explored for determining the youngest stellar populations. This thesis aims to quantify these young stellar populations by using spectral absorption features of massive ETGs. We exploit state-of-the-art stellar population models based on empirical stellar libraries to analyse, for the first time, observed optical and near-UV line-strength indices simultaneously. We compare observations with model predictions from two assumed simple parameterisations of the star formation history (SFH) of massive galaxies. We first explore if the residual star formation is ubiquitous among the massive ETG population by stacking thousands of galaxy spectra at redshift of z ∼ 0.4. We derive mass fractions of the young stellar component as a function of mass. We find that massive galaxies show, on average, a sub-one percent fraction of young stars formed within the last 2 Gyr, and that this fraction is larger for less massive galaxies. This trend with mass is consistent with the fact that less massive galaxies have more extended SFHs than their more massive counterparts and also may be related to the fact that AGN feedback stops the formation of new stars more efficiently for more massive galaxies. We also find that synthetic massive galaxies from cosmological numerical simulations significantly overproduce both intermediate and young stellar populations. This means that the recipe to quench the star formation in these galaxies, and perhaps to maintain them quenched, still needs to be fully understood. However, the results obtained here put stringent constrains that must be satisfied by these simulations. In order to understand the origin of these young stars, we turned to spatially resolved spectroscopy to tell us precisely where they are located. For this purpose, we analyse a special type of ETGs: the brightest cluster galaxies (BCGs). These galaxies are located in the centres of the gravitational potential wells of galaxy clusters. Our study of 6 nearby BCGs indicate that their young stars are located within < 2 kpc of the galaxy centres, i.e. in their cores. Our findings of small young mass fractions are consistent with being formed in-situ, likely residual star formation from recycled material of dying stars from previous generations. However, due to the particular location of these massive systems, an ex-situ origin through environmental processes can not be ruled out. The study of young stellar components in so-called ”relic galaxies” offers us unique clues to understand the possible origins of the recent star formation that we detect in normal ETGs. These massive compact relic galaxies are thought to have survived untouched since their formation at high-z until the presentday, i.e. without having gone through a second phase that is characterised by a growth in size and mass by accretion. For this purpose, we studied the young stellar contribution in the 1 kpc central region of NGC 1277, a well studied galaxy that is regarded as the prototypical relic galaxy in the nearby Universe. We find a sub-one percent level of young mass fractions, similar to our samples of massive ETGs, which points to intrinsic, in-situ, processes that trigger the formation of these young stars

Pond Characteristics and Occupancy by Red-Necked Phalaropes in the Mackenzie Delta, Northwest Territories, Canada

Red-necked phalaropes (Phalaropus lobatus) breed in Arctic and Subarctic lowlands throughout the circumpolar region. They are highly reliant on shallow freshwater ponds for social interaction, copulation, and foraging for small aquatic invertebrates. Threats related to warmer continental temperatures could lead to encroachment of shrub vegetation and premature drying of wetlands that serve as breeding habitat. We documented patterns of pond use over the breeding season and investigated pond characteristics associated with high occupancy by red-necked phalaropes. Research was conducted during two breeding seasons in a large wetland on Niglintgak Island, located in the mouth of the Mackenzie Delta, Northwest Territories. The frequency of pond occupancy declined between the onset of incubation and average hatch dates. Neither invertebrate assemblages (potential prey) nor physical characteristics (water chemistry and vegetation characteristics) varied significantly between ponds categorized as high-use, low-use, and no-use, in either year. Dry weight of potential prey (g/m3) was higher during the incubation period than during the nest initiation period. Pond occupancy both prior to and during incubation showed a clumped distribution, suggesting that choice of ponds was related in part to social stimulation. Future studies should examine the proximity of ponds to nest sites, the effects of premature drying of ponds on food availability, the distribution of resources surrounding ponds, and the occupancy of ponds by broods during the period preceding fall migration.Les phalaropes à bec étroit (Phalaropus lobatus) se reproduisent dans les basses terres arctiques et subarctiques à l’échelle de la région circumpolaire. Ils dépendent beaucoup des étangs d’eau douce peu profonds car c’est là que se passent leur interaction sociale, la copulation et la consommation de petits invertébrés aquatiques. Les menaces liées au réchauffement des températures continentales pourraient se traduire par un empiètement sur la végétation d’arbrisseaux et l’assèchement prématuré des terrains marécageux qui servent d’habitat de reproduction. Nous avons documenté les tendances d’utilisation des étangs pendant la saison de reproduction et avons analysé les caractéristiques des étangs fréquentés par de grands nombres de phalaropes à bec étroit. Notre recherche a été effectuée pendant deux saisons de reproduction sur une vaste zone marécageuse de l’île Niglintgak, située à l’embouchure du delta du Mackenzie, dans les Territoires du Nord-Ouest. La fréquence de l’achalandage aux étangs chutait entre le début de l’incubation et les dates d’éclosion moyennes. Ni les assemblages d’invertébrés (proies potentielles) ni les caractéristiques physiques (chimie de l’eau et caractéristiques de la végétation) variaient considérablement entre les étangs classés comme étangs achalandés, étangs moins achalandés ou étangs pas achalandés du tout, pendant l’une ou l’autre des années. Le poids sec des proies potentielles (g/m3) était plus élevé pendant la période d’incubation que pendant la période d’initiation du nid. La répartition de l’achalandage des étangs avant et pendant l’incubation était contagieuse, ce qui laisse croire que le choix d’étang se faisait, en partie, en fonction de la stimulation sociale. Les études effectuées à l’avenir devraient examiner la proximité des étangs aux nids, les effets de l’assèchement prématuré des étangs sur la disponibilité de nourriture, la répartition des ressources entourant les étangs et l’achalandage des étangs par les couvées pendant la période précédant la migration automnale

Efficient Hardware Acceleration of Robust Volumetric Light Transport Simulation

Efficiently simulating the full range of light effects in arbitrary input scenes that contain participating media is a difficult task. Unified points, beams and paths (UPBP) is an algorithm capable of capturing a wide range of media effects, by combining bidirectional path tracing (BPT) and photon density estimation (PDE) with multiple importance sampling (MIS). A computationally expensive task of UPBP is the MIS weight computation, performed each time a light path is formed. We derive an efficient algorithm to compute the MIS weights for UPBP, which improves over previous work by eliminating the need to iterate over the path vertices. We achieve this by maintaining recursive quantities as subpaths are generated, from which the subpath weights can be computed. In this way, the full path weight can be computed by only using the data cached at the two vertices at the ends of the subpaths. Furthermore, a costly part of PDE is the search for nearby photon points and beams. Previous work has shown that a spatial data structure for photon mapping can be implemented using the hardware-accelerated bounding volume hierarchy of NVIDIA's RTX GPUs. We show that the same technique can be applied to different types of volumetric PDE and compare the performance of these data structures with the state of the art. Finally, using our new algorithm and data structures we fully implement UPBP on the GPU which we, to the best of our knowledge, are the first to do so

Responses of Syrphids, Elaterids and Bees to Single-tree Selection Harvesting in Algonquin Provincial Park, Ontario

The species composition of hoverflies (Syrphidae), click beetles (Elateridae), and bees (Apoidea) was studied to determine whether there was a positive response in these flower-seeking insect groups to gaps in the canopy created through single-tree selection harvesting of Sugar Maple (Acer saccharum) and Yellow Birch (Betula alleghaniensis) in hardwood forests of the Great Lakes-St. Lawrence forest region of Algonquin Provincial Park, Ontario. There were significantly more hoverflies and bees collected in forest stands harvested within the previous five years than in wilderness zone (unharvested at least for 40 years) stands or stands harvested 15-20 years previously (old logged stands). Click beetles, especially Selatosomus pulcher (LeConte), were collected most often in old logged stands. Bees and click beetles were collected significantly later in the season in logged than in wilderness zone stands. Malaise traps resulted in higher capture rates for syrphids than pan traps, and only with these higher capture rates did we detect a significant increase in species richness in recently logged stands over that in wilderness stands. Changes in the numbers and phenology of flower-visiting insects may impact on reproductive success of flowering plants of the forest understory and deserves further study

Experimental Infection of Richardson’s Ground Squirrels (\u3ci\u3eSpermophilus Richardsonii\u3c/i\u3e ) With Attenuated and Virulent Strains pf \u3ci\u3eBrucella abortus\u3c/i\u3e

A previous investigation of the safety of Brucella abortus strain RB51 (sRB51) in various nontarget species suggested that Richardson’s ground squirrels (Spermophilus richardsonii) may develop persistent infections when orally inoculated with the vaccine. In the present study, sRB51, B. abortus strain 19 (s19), and virulent B. abortus strain 9941 (s9941) were administered orally to Richardson’s ground squirrels to further characterize B. abortus infection in this species. Six groups of nongravid ground squirrels were orally inoculated with 6x108 colony forming units (cfu) sRB51 (n=10), 2.5x104 cfu s19 (n=10), 2.5x107 cfu s19 (n=6), 1.3x106 cfu s9941 (n=5), 2.1x108 cfu s9941 (n=5), or vaccine diluent (control; n=4). One of five animals in the lower-dose s19 group and two of three animals in the higher-dose s19 group showed persistence of bacteria in various tissues at 14 wk post-inoculation (PI). At 18 wk PI, one of five animals in the sRB51 group and one of five animals in the high-dose s9941 group were culture positive. Although we did detect some persistence of B. abortus strains at 18 wk, we found no evidence of pathology caused by B. abortus strains in nonpregnant Richardson’s ground squirrels based on clinical signs, gross lesions, and microscopic lesions

Influence of irrigation on yield and grain quality of maize hybrids (Zea mays L.)

Istraživanje je provedeno na pokušalištu Poljoprivrednog instituta iz Osijeka 2015. godine. Cilj istraživanja bio je ispitati utjecaj tretmana navodnjavanja (a1-kontrolni tretman, a2-kukuruz je navodnjavan tako da se sadržaj vode u tlu održava na razini od 60-100% PVK i a3-80-100% PVK) na urod i kvalitetu zrna kukuruza (b1 = OSSK596; b2 = OSSK617; b3 = OSSK665; b4 = OSSK552). Navodnjavanje kukuruza obavljeno je metodom kišenja, samohodnim rasprskivačem „Typhon“. Trenutak početka navodnjavanja određen je direktnom metodom elektrometrije. Navodnjavanje je vrlo značajno (p<0,01) povećalo urod zrna kukuruza (a1 = 8,48 t/ha; a3 = 9,42 t/ha), broj zrna na klipu (a1 = 567; a3 = 594), te značajno (p<0,05) masu zrna (a1 = 1030 g; a3 = 1094 g). Hibrid je vrlo značajno (p<0,01) utjecao na urod zrna kukuruza (b2 = 7,61 t/ha; b1 = 9,64 t/ha), apsolutnu masu (b4 = 333; b2 i b3 = 363 g), masu zrna kukuruza (b4 = 994 g; b2 = 1106 g), broj zrna na klipu (b3 = 558; b1 = 602). Interakcija navodnjavanja i hibrida (a x b) značajno je utjecala na broj zrna na klipu (a1b3 = 527; a1b1 = 617). Slaba korelacijska veza pozitivnoga smjera bila je između uroda i broja zrna u redu (r=0,303*), zatim između uroda i mase zrna (r=0,498*), između uroda i randmana (r=0,484*) te između uroda i apsolutne mase zrna (r=0,329*).The field research was set up at the trial field of Agricultural institute in Osijek during growing season 2015. The main objective of this research was to study the influence of different irrigation treatment (a1-rainfed, a2- 60-100% field water capacity, FWC and a3-80-100% FWC) and maize hybrids (b1 = OSSK596; b2 = OSSK617; b3 = OSSK665; b4 = OSSK552) on yield and quality of maize grain. The maize crop was irrigated with traveling gun, sprinkler system. Time of irrigation event was determined by direct measuring of soil water content (gypsum block). Irrigation treatment significantly (p<0.01) increased yield of maize grain (a1 = 8.48 t/ha; a3 = 9.42 t/ha), grain number per cob (a1 = 567; a3 = 594), while significantly (p<0.05) grain weight (a1 = 1030 g; a3 = 1094 g). The influence of maize hybrid was significant for yield of maize grain (b2 = 7.61 t/ha; b1 = 9.64 t/ha), 1000 grain weight (b4 = 333; b2 and b3 = 363 g), grain weight (b4 = 994 g; b2 = 1106 g), grain number per cob (b3 = 558; b1 = 602). Irrigation x hybrid (a x b) interaction was significant for grain number per cob (a1b3 = 527; a1b1 = 617). The analysis of interaction showed weak and positive correlation between yield and grain number (r=0.303*); yield and grain weight (0.498*) and between yield and 1000 grain weight (0.329*)

Summary of Northern Europe as a role model:successful enterprise in a globalising economy

Does Northern Europe possess unique characteristics that cannot disappear and do not need to disappear, or will globalisation inevitably result in uniformity, divested businesses, lower wages and huge pressure on social security provisions? This is one of the main questions addressed by the authors. The authors examine how companies respond to global developments. They also discuss the implications of these developments for entrepreneurs and whether knowledge institutions and governments play a part in creating a climate that is conducive to enterprise. They consider these issues from the perspective of different regions. Each region has its own distinct regional characteristics and its own distinct regional views on particular issues. As well as endeavouring to describe the key macroeconomic characteristics, they also consider how (entrepreneurial and policy-making) organisations should respond to the current macroeconomic challenges