Testing Spatial Autocorrelation in Weighted Networks : the Modes Permutation Test

In a weighted spatial network, as specified by an exchange matrix, the variances of the spatial values are inversely proportional to the size of the regions. Spatial values are no more exchangeable under independence, thus weakening the rationale for ordinary permutation and bootstrap tests of spatial autocorrelation. We propose an alternative permutation test for spatial autocorrelation, based upon exchangeable spatial modes, constructed as linear orthogonal combinations of spatial values. The coefficients obtain as eigenvectors of the standardised exchange matrix appearing in spectral clustering, and generalise to the weighted case the concept of spatial filtering for connectivity matrices. Also, two proposals aimed at transforming an acessibility matrix into a exchange matrix with with a priori fixed margins are presented. Two examples (inter-regional migratory flows and binary adjacency networks) illustrate the formalism, rooted in the theory of spectral decomposition for reversible Markov chains.

Combined analysis of grey matter voxel-based morphometry and white matter tract-based spatial statistics in late-life bipolar disorder.

Background: Previous magnetic resonance imaging (MRI) studies in young patients with bipolar disorder indicated the presence of grey matter concentration changes as well as microstructural alterations in white matter in various neocortical areas and the corpus callosum. Whether these structural changes are also present in elderly patients with bipolar disorder with long-lasting clinical evolution remains unclear. Methods: We performed a prospective MRI study of consecutive elderly, euthymic patients with bipolar disorder and healthy, elderly controls. We conducted a voxel-based morphometry (VBM) analysis and a tract-based spatial statistics (TBSS) analysis to assess fractional anisotropy and longitudinal, radial and mean diffusivity derived by diffusion tensor imaging (DTI). Results: We included 19 patients with bipolar disorder and 47 controls in our study. Fractional anisotropy was the most sensitive DTI marker and decreased significantly in the ventral part of the corpus callosum in patients with bipolar disorder. Longitudinal, radial and mean diffusivity showed no significant between-group differences. Grey matter concentration was reduced in patients with bipolar disorder in the right anterior insula, head of the caudate nucleus, nucleus accumbens, ventral putamen and frontal orbital cortex. Conversely, there was no grey matter concentration or fractional anisotropy increase in any brain region in patients with bipolar disorder compared with controls. Limitations: The major limitation of our study is the small number of patients with bipolar disorder. Conclusion: Our data document the concomitant presence of grey matter concentration decreases in the anterior limbic areas and the reduced fibre tract coherence in the corpus callosum of elderly patients with long-lasting bipolar disorder.

Variations in national management accounting approaches

During the 1990's studies of management accounting practices in Europe and in Latin America have given us data on 23 countries. In this paper we use this data to identify five distinct aspects of national management accounting culture being:1. The influence of regulations on official recommendations;2. The source of management accountants;3. Influence from one country to another;4. Variations in use of specific techniques;5. Variations in the objectives of the management accounting system.We then identify seven significant implications of the manager operating in the multinational environment.

Variations in IB1/JIP1 expression regulate susceptibility of beta-cells to cytokine-induced apoptosis irrespective of C-Jun NH2-terminal kinase signaling.

We previously reported that interleukin-1beta (IL-1beta) alone does not cause apoptosis of beta-cells, whereas when combined with gamma-interferon (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha), it exerts a distinct apoptotic effect. Studies in beta-cell lines indicated that IL-1beta reduced expression of islet brain (IB)-1/JNK interacting protein (JIP)-1, a JNK scaffold protein with antiapoptotic action. We examined whether variations in IB1/JIP-1 expression in purified primary beta-cells affect their susceptibility to cytokine-induced apoptosis. Exposure to IL-1beta for 24 h decreased cellular IB1/JIP-1 content by 66 +/- 17%; this IL-1beta effect was maintained in the presence of TNF-alpha + IFN-gamma, which did not influence IB1/JIP-1 levels by themselves. Addition of IL-1beta to TNF-alpha + IFN-gamma increased apoptosis from 20 +/- 2% to 59 +/- 5%. A similar increase in TNF-alpha + IFN-gamma-induced apoptosis was produced by adenoviral expression of antisense IB1/JIP-1 and was not further enhanced by addition of IL-1beta, indicating that IL-1beta-mediated suppression of IB1/JIP-1 in beta-cells increases their susceptibility to cytokine-induced apoptosis. However, adenovirally mediated overexpression of IB1/JIP-1 also potentiated TNF-alpha + IFN-gamma-induced apoptosis, suggesting that the antiapoptotic effect of IB1/JIP-1 depends on well-defined cellular levels. We conclude that the IB1/JIP-1 level in beta-cells can control their susceptibility to apoptosis independent of JNK signaling.

Impact of small variations in temperature and humidity on the reproductive activity and survival of Aedes aegypti (Diptera, Culicidae)

In short space of time increase in temperature and rainfall can affect vector populations and, consequently, the diseases for them transmitted. The present study analyzed the effect of small temperature and humidity variations on the fecundity, fertility and survival of Aedes aegypti. These parameters were analyzed using individual females at temperatures ranging from 23 to 27 °C (mean 25 °C); 28 to 32 °C (mean 30 °C) and 33 to 37 °C (mean 35 ºC) associated to 60±8% and 80±6% relative humidity. Females responded to an increase in temperature by reducing egg production, oviposition time and changing oviposition patterns. At 25 ºC and 80% relative humidity, females survived two-fold more and produced 40% more eggs when compared to those kept at 35 ºC and 80% relative humidity. However, in 45% of females kept at 35 ºC and 60% relative humidity oviposition was inhibited and only 15% females laid more than 100 eggs, suggesting that the intensity of the temperature effect was influenced by humidity. Gradual reductions in egg fertility at 60% relative humidity were observed with the increase in temperature, although such effect was not found in the 80% relative humidity at 25 º C and 30 º C. These results suggest that the reduction in population densities recorded in tropical areas during seasons when temperatures reach over 35 ºC is likely to be strongly influenced by temperature and humidity, with a negative effect on several aspects of mosquito biology.

Environmental factors giving rise to variations in national management accounting practice

Comparative national management accounting is the least developed aspect in the field of international accounting. Only during the second half of the 1990's some comparisons of national managementaccounting practice have appeared published but only at theregional level. In this paper a range of factors that give rise to variations in national management accounting practice are postulated. We support this list with examples from a range of analyses of national management accounting practices, drawing particularly on the work of Lizcano (1996) and Bhimani (1996).Finally, twelve key factors are identified as influencing an individual country's approach to management accounting.

Regional variations in ABC transporter expression along the mouse intestinal tract.

The ATP-binding cassette (ABC) family of proteins comprise a group of membrane transporters involved in the transport of a wide variety of compounds, such as xenobiotics, vitamins, lipids, amino acids, and carbohydrates. Determining their regional expression patterns along the intestinal tract will further characterize their transport functions in the gut. The mRNA expression levels of murine ABC transporters in the duodenum, jejunum, ileum, and colon were examined using the Affymetrix MuU74v2 GeneChip set. Eight ABC transporters (Abcb2, Abcb3, Abcb9, Abcc3, Abcc6, Abcd1, Abcg5, and Abcg8) displayed significant differential gene expression along the intestinal tract, as determined by two statistical models (a global error assessment model and a classic ANOVA, both with a P < 0.01). Concordance with semiquantitative real-time PCR was high. Analyzing the promoters of the differentially expressed ABC transporters did not identify common transcriptional motifs between family members or with other genes; however, the expression profile for Abcb9 was highly correlated with fibulin-1, and both genes share a common complex promoter model involving the NFkappaB, zinc binding protein factor (ZBPF), GC-box factors SP1/GC (SP1F), and early growth response factor (EGRF) transcription binding motifs. The cellular location of another of the differentially expressed ABC transporters, Abcc3, was examined by immunohistochemistry. Staining revealed that the protein is consistently expressed in the basolateral compartment of enterocytes along the anterior-posterior axis of the intestine. Furthermore, the intensity of the staining pattern is concordant with the expression profile. This agrees with previous findings in which the mRNA, protein, and transport function of Abcc3 were increased in the rat distal intestine. These data reveal regional differences in gene expression profiles along the intestinal tract and demonstrate that a complete understanding of intestinal ABC transporter function can only be achieved by examining the physiologically distinct regions of the gut.

Local-scale spatial variation in diversity of social wasps in an Amazonian rain forest in Caxiuanã, Pará, Brazil (Hymenoptera, Vespidae, Polistinae)

Polistine wasps are important in Neotropical ecosystems due to their ubiquity and diversity. Inventories have not adequately considered spatial attributes of collected specimens. Spatial data on biodiversity are important for study and mitigation of anthropogenic impacts over natural ecosystems and for protecting species. We described and analyzed local-scale spatial patterns of collecting records of wasp species, as well as spatial variation of diversity descriptors in a 2500-hectare area of an Amazon forest in Brazil. Rare species comprised the largest fraction of the fauna. Close range spatial effects were detected for most of the more common species, with clustering of presence-data at short distances. Larger spatial lag effects could also be identified in some species, constituting probably cases of exogenous autocorrelation and candidates for explanations based on environmental factors. In a few cases, significant or near significant correlations were found between five species (of Agelaia, Angiopolybia, and Mischocyttarus) and three studied environmental variables: distance to nearest stream, terrain altitude, and the type of forest canopy. However, association between these factors and biodiversity variables were generally low. When used as predictors of polistine richness in a linear multiple regression, only the coefficient for the forest canopy variable resulted significant. Some level of prediction of wasp diversity variables can be attained based on environmental variables, especially vegetation structure. Large-scale landscape and regional studies should be scheduled to address this issue.

Iowa Fisheries Research Technical Series No. 75-1 Variations in the abundance of channel catfish year classes in the upper Mississippi River and causative factors Don R. Helms, Fishery Research Biologist Fisheries Section Jerry M. Conley, Superintendent of Fisheries December, 1975

study of channel catfish in the Mississippi River to determine differences in year class abundance and causative factors

Variations in fathers' discourse on fatherhood and in family alliances during infancy

The aim of this pilot study is to analyse the discourse of fathers of toddlers concerning fatherhood and the link between some particularities in the discourse and family alliance. The sample consists of 13 Swiss first time fathers (5 fathers of girls and 8 of boys). In order to evaluate the paternal discourse, the fathers were given a semi-structured interview, which was later analysed using the research package Alceste. The family alliance, i.e., the degree of coordination among the partners when executing a task together, was assessed through the Lausanne Trilogue Play (Fivaz-Depeursinge & Corboz-Warnery, 1999). The main results indicated an interesting link between classes of paternal discourse grouped around the following themes "affective relationship", "daily routine" and "educational goals", and the family alliance (defined in two major categories; functional and problematic alliances). Finally, clinical perspectives on links between paternal representations and family functioning at an interactive level are discussed

The effect of non-medical factors on variations in the performance of colonoscopy among different health care settings

BACKGROUND: Previous published studies have shown significant variations in colonoscopy performance, even when medical factors are taken into account. This study aimed to examine the role of nonmedical factors (ie, embodied in health care system design) as possible contributors to variations in colonoscopy performance. METHODS: Patient data from a multicenter observational study conducted between 2000 and 2002 in 21 centers in 11 western countries were used. Variability was captured through 2 performance outcomes (diagnostic yield and colonoscopy withdrawal time), jointly studied as dependent variables, using a multilevel 2-equation system. RESULTS: Results showed that open-access systems and high-volume colonoscopy centers were independently associated with a higher likelihood of detecting significant lesions and longer withdrawal durations. Fee for service (FFS) payment was associated with shorter withdrawal durations, and so had an indirect negative impact on the diagnostic yield. Teaching centers exhibited lower detection rates and longer withdrawal times. CONCLUSIONS: Our results suggest that gatekeeping colonoscopy is likely to miss patients with significant lesions and that developing specialized colonoscopy units is important to improve performance. Results also suggest that FFS may result in a lower quality of care in colonoscopy practice and highlight the fact that longer withdrawal times do not necessarily indicate higher quality in teaching centers.

Public health expenditure and spatial interactions in a decentralized national health system

One of the limitations of cross-country health expenditure analysis refers to the fact that the financing, the internal organization and political restraints of health care decision-making are country-specific and heterogeneous. Yet, a potential solution is to examine the influence of such effects in those countries that have undertaken decentralization processes. In such a setting, it is possible to examine potential expenditure spillovers across the geography of a country as well as the influence of the political ideology of regional incumbents on public health expenditure. This paper examines the determinants of public health expenditure within Spanish region-states (Autonomous Communities, ACs), most of them subject to similar financing structures although exhibiting significant heterogeneity as a result of the increasing decentralization, region-specific political factors along with different use of health care inputs, economic dimension and spatial interactions

Public health expenditure and spatial interactions in a decentralized national health system

One of the limitations of cross-country health expenditure analysis refers to the fact that the financing, the internal organization and political restraints of health care decision-making are country-specific and heterogeneous. Yet, a potential solution is to examine the influence of such effects in those countries that have undertaken decentralization processes. In such a setting, it is possible to examine potential expenditure spillovers across the geography of a country as well as the influence of the political ideology of regional incumbents on public health expenditure. This paper examines the determinants of public health expenditure within Spanish region-states (Autonomous Communities, ACs), most of them subject to similar financing structures although exhibiting significant heterogeneity as a result of the increasing decentralization, region-specific political factors along with different use of health care inputs, economic dimension and spatial interactions

Testing Spatial Autocorrelation in Weighted Networks : the Modes Permutation Test

In a weighted spatial network, as specified by an exchange matrix, the variances of the spatial values are inversely proportional to the size of the regions. Spatial values are no more exchangeable under independence, thus weakening the rationale for ordinary permutation and bootstrap tests of spatial autocorrelation. We propose an alternative permutation test for spatial autocorrelation, based upon exchangeable spatial modes, constructed as linear orthogonal combinations of spatial values. The coefficients obtain as eigenvectors of the standardised exchange matrix appearing in spectral clustering, and generalise to the weighted case the concept of spatial filtering for connectivity matrices. Also, two proposals aimed at transforming an acessibility matrix into a exchange matrix with with a priori fixed margins are presented. Two examples (inter-regional migratory flows and binary adjacency networks) illustrate the formalism, rooted in the theory of spectral decomposition for reversible Markov chains.