A Note on Z_2 Symmetries of the KZ Equation

We continue the study of hidden Z_2 symmetries of the four-point sl(2)_k Knizhnik-Zamolodchikov equation iniciated in hep-th/0508019. Here, we focus our attention on the four-point correlation function in those cases where one spectral flowed state of the sector w=1 is involved. We give a formula that shows how this observable can be expressed in terms of the four-point function of non spectral flowed states. This means that the formula holding for the winding violating four-string scattering processes in AdS_3 has a simple expression in terms of the one for the conservative case, generalizing what is known for the case of three-point functions, where the violating and the non-violating structure constants turn out to be connected one to each other in a similar way. What makes this connection particularly simple is the fact that, unlike what one would naively expect, it is not necessary to explicitly solve the five-point function containing a single spectral flow operator to this end. Instead, non diagonal functional relations between different solutions of the KZ equation turn out to be the key point for this short path to exist. Considering such functional relation is necessary but it is not sufficient; besides, the formula also follows from the relation existing between correlators in both WZNW and Liouville conformal theories.Comment: 24 pages. Minor changes and references added; version accepted for publicatio

Study of Ultraviolet-Induces Chromatid and Chromosome Aberrations as a Function of Dose in G1 Phase Vertebrate Tissue Cultures

G1 phase A8 Xenopus laevis (toad) and V79B Cricetulus griseus (hamster) tissue cultures were used to observe the frequency of ultraviolet-induced chromosomal aberrations as a function of dose. When cultures are irradiated with ultraviolet light, visible aberrations are virtually absent until a threshold of approximately 80 ergs mm⁻¹ is reached. Aberrations then occur as a nonlinear function of dose. Chromatid aberrations are by far the most prevalent until doses in excess of 200 ergs mm⁻¹ are administered, at which point chromosome aberrations become common

Social Insurance and Manpower Policy in the Soviet Union

Paper presented at the November 1961 meeting of the Southern Economic Association in Atlanta, Georgi

Towards systematic conservation planning in the Azores

Several field methodologies, analytical measures and theoretical patterns have been explored for conservation planning for arthropods in native forests of the Azores archipelago. Here, the outcomes are assembled to make recommendations on practical strategies to assess arthropod diversity and to select and manage protected native forests in the Azores. Suggestions are made on how to apply similar plans for conservation of other plant and animal groups in these forests. Potential threats to the Azorean native forest are described and measures to minimize them are proposed. Future studies are also suggested that would improve the present knowledge of arthropod diversity and distribution in Azorean native forests and could assist in the identification of suitable conservation strategies

Arthropods as surrogates of diversity at different spatial scales

Copyright © 2010 Elsevier Ltd. All rights reserved.This study evaluates the effectiveness of taxonomic, colonization and trophic groups of arthropods from native forests of the Azores archipelago as surrogates of the diversity of other arthropod groups and of the remaining arthropods. Consistency in the performance of surrogates was tested across three spatial scales and using two measures of diversity. Pitfall and beating samples from 109 transects, 18 forest fragments and seven islands were analysed. The results showed that Araneae, Hemiptera and small orders taxonomic groups; native, endemic and introduced colonization groups; and the herbivores trophic group were consistent surrogates of the remaining diversity across the three spatial scales analysed, for both alpha and dissimilarity diversities. However, none of the subsets considered was significantly related with all of the other subsets at any of the three spatial scales. The effectiveness of surrogacy was dependent on the spatial level considered, and groups behaved inconsistently depending on the measure of diversity used. The value of a group as a diversity surrogate should be evaluated for a study area for a given spatial scale and diversity measure, in accordance with the scale and measure that will be used for biodiversity assessments and monitoring programs in that area

Diversity and distribution of arthropods in native forests of the Azores archipelago

Since 1999, our knowledge of arthropods in native forests of the Azores has improved greatly. Under the BALA project (Biodiversity of Arthropods of Laurisilva of the Azores), an extensive standardised sampling protocol was employed in most of the native forest cover of the Archipelago. Additionally, in 2003 and 2004, more intensive sampling was carried out in several fragments, resulting in nearly a doubling of the number of samples collected. A total of 6,770 samples from 100 sites distributed amongst 18 fragments of seven islands have been collected, resulting in almost 140,000 specimens having been caught. Overall, 452 arthropod species belonging to Araneae, Opilionida, Pseudoscorpionida, Myriapoda and Insecta (excluding Diptera and Hymenoptera) were recorded. Altogether, Coleoptera, Hemiptera, Araneae and Lepidoptera comprised the major proportion of the total diversity (84%) and total abundance (78%) found. Endemic species comprised almost half of the individuals sampled. Most of the taxonomic, colonization, and trophic groups analysed showed a significantly left unimodal distribution of species occurrences, with almost all islands, fragments or sites having exclusive species. Araneae was the only group to show a strong bimodal distribution. Only a third of the species was common to both the canopy and soil, the remaining being equally exclusive to each stratum. Canopy and soil strata showed a strongly distinct species composition, the composition being more similar within the same stratum regardless of the location, than within samples from both strata at the same location. Possible reasons for these findings are explored. The procedures applied in the sampling protocol are also discussed

Arthropods as surrogates of diversity at different spatial scales

Copyright © 2010 Elsevier Ltd. All rights reserved.This study evaluates the effectiveness of taxonomic, colonization and trophic groups of arthropods from native forests of the Azores archipelago as surrogates of the diversity of other arthropod groups and of the remaining arthropods. Consistency in the performance of surrogates was tested across three spatial scales and using two measures of diversity. Pitfall and beating samples from 109 transects, 18 forest fragments and seven islands were analysed. The results showed that Araneae, Hemiptera and small orders taxonomic groups; native, endemic and introduced colonization groups; and the herbivores trophic group were consistent surrogates of the remaining diversity across the three spatial scales analysed, for both alpha and dissimilarity diversities. However, none of the subsets considered was significantly related with all of the other subsets at any of the three spatial scales. The effectiveness of surrogacy was dependent on the spatial level considered, and groups behaved inconsistently depending on the measure of diversity used. The value of a group as a diversity surrogate should be evaluated for a study area for a given spatial scale and diversity measure, in accordance with the scale and measure that will be used for biodiversity assessments and monitoring programs in that area

Selection of priority areas for arthropod conservation in the Azores archipelago

Copyright © Springer Science+Business Media B.V. 2010.The largest standardised database available to date for arthropods in native forests of the Azores archipelago was used to determine the minimum optimal set of native forest fragments needed to accomplish four different targets of species occurrence (presence-absence) and abundance (20, 50 and 80%) using different groups of arthropods and all data combined. The results showed that occurrence and 20% abundance targets gave similar optimal solutions for most of the groups considered. At least one fragment on each of the seven studied islands was required to accomplish any occurrence and abundance target. To achieve 80% of abundance for all species, all fragments were necessary and to guarantee 50% of the overall abundance of endemics, 17 out of 18 native forests were needed. A suggestion is made to apply a measure of biotic integrity related to disturbance to select, among alternative optimal solutions, the set of areas that will help to guarantee the viability of populations. Some guidelines for the selection of priority areas for conservation in the Azores are presented

Abundance, spatial variance and occupancy: arthropod species distribution in the Azores

Copyright © 2006 British Ecological Society.1. The positive abundance-occupancy and abundance-variance relationships are two of the most widely documented patterns in population and community ecology. 2. Recently, a general model has been proposed linking the mean abundance, the spatial variance in abundance, and the occupancy of species. A striking feature of this model is that it consists explicitly of the three variables abundance, variance and occupancy, and no extra parameters are involved. However, little is known about how well the model performs. 3. Here, we show that the abundance-variance-occupancy model fits extremely well to data on the abundance, variance and occupancy of a large number of arthropod species in natural forest patches in the Azores, at three spatial extents, and distinguishing between species of different colonization status. Indeed, virtually all variation about the bivariate abundance-occupancy and abundance-variance relationships is effectively explained by the third missing variable (variance in abundance in the case of the abundance-occupancy relationship, and occupancy in the case of the abundance-variance relationship). 4. Introduced species tend to exhibit lower densities, less spatial variance in these densities, and occupy fewer sites than native and endemic species. None the less, they all lie on the same bivariate abundance-occupancy and abundance-variance, and trivariate abundance-variance-occupancy, relationships. 5. Density, spatial variance in density, and occupancy appear to be all the things one needs to know to describe much of the spatial distribution of species