Aggregation of metallochlorophylls - Examination by spectroscopy

Nuclear magnetic resonance measurements determine which metallochlorophylls, besides magnesium-containing chlorophylls, possess coordination aggregation properties. Infrared spectroscopy reveals that only zinc pheophytin and zinc methyl pheophorbide showed significant coordination aggregation, whereas divalent nickel and copper did not

A study to determine similarities and variances among medical-surgical nursing instructors in rating selected science principles underlying the nursing care of a patient with an ileostomy

Thesis (M.S.)--Boston Universit

Constructing Amplitudes from Their Soft Limits

The existence of universal soft limits for gauge-theory and gravity amplitudes has been known for a long time. The properties of the soft limits have been exploited in numerous ways; in particular for relating an n-point amplitude to an (n-1)-point amplitude by removing a soft particle. Recently, a procedure called inverse soft was developed by which "soft" particles can be systematically added to an amplitude to construct a higher-point amplitude for generic kinematics. We review this procedure and relate it to Britto-Cachazo-Feng-Witten recursion. We show that all tree-level amplitudes in gauge theory and gravity up through seven points can be constructed in this way, as well as certain classes of NMHV gauge-theory amplitudes with any number of external legs. This provides us with a systematic procedure for constructing amplitudes solely from their soft limits.Comment: minor change

How perilous are broad-scale correlations with environmental variables?

Many studies correlate geographic variation of biotic variables (e.g., species ranges, species richness, etc.) with variation in environmental variables (climate, topography, history). Often, the resulting correlations are interpreted as evidence of causal links. However, both the dependent and independent variables in these analyses are strongly spatially structured. Several studies have suggested that spatially structured variables may be significantly correlated with one another despite the absence of a causal link between them. In this study we ask: if two variables are spatially structured, but causally unrelated, how strong is the expected correlation between them? As a specific example, we consider the correlations between broad-scale variation in gamma species richness and climatic variables. Are these correlations likely to be statistical artefacts? To answer these questions, we randomly generated pseudo-climatic variables that have the same range and spatial autocorrelation as temperature and precipitation in the Americas. We related mammal and bird species richness both to the real and the pseudo-climatic variables. We also observed the correlations among pseudo-climate simulations. Correlations among randomly generated, spatially unstructured, variables are very small. In contrast, the median correlations between spatially structured variables are near r2=0.1 – 0.3, and the 95% confidence limits extend to r2=0.6 – 0.7. Viewing this as a null expectation, given spatially structured variables, it is worth nothing that published richness–climate correlations are typically marginally stronger than these values. However, many other published richness–environment correlations would fail this test. Tests of the “predictive ability” of a correlation cannot reliably distinguish correlations due to spatial structure from causal relationships. Our results suggest a three-part update of Tobler’s “First Law of Geography”: #1) Everything in geography that is spatially structured will be collinear. #2) Near things are more related than distant things. #3) The more strongly spatially structured two variables are, the stronger the collinearity between them will be

The temporal binding deficit hypothesis of autism

Frith has argued that people with autism show “weak central coherence,” an unusual bias toward piecemeal rather than configurational processing and a reduction in the normal tendency to process information in context. However, the precise cognitive and neurological mechanisms underlying weak central coherence are still unknown. We propose the hypothesis that the features of autism associated with weak central coherence result from a reduction in the integration of specialized local neural networks in the brain caused by a deficit in temporal binding. The visuoperceptual anomalies associated with weak central coherence may be attributed to a reduction in synchronization of high-frequency gamma activity between local networks processing local features. The failure to utilize context in language processing in autism can be explained in similar terms. Temporal binding deficits could also contribute to executive dysfunction in autism and to some of the deficits in socialization and communication

Land Markets, Employment, and Resource Use in the Peri-Urban Green Zones of Maputo, Mozambique: A Case Study of Land Market Rigidities and Institutional Constraints to Economic Growth

Beginning in January 1991, the U.S. Agency for International Development funded a series of studies on land, employment, and financial markets in the peri-urban areas of Maputo. Beginning in September 1991, a land-market survey involving 121 households and 162 plots of land was administered in two peri-urban green zones of Maputo-districts 4 and 6. Households were queried about their land-settlement histories, mode of land acquisition, terms and conditions of transfer, land rights, size of holdings, perceptions of tenure security, land-use practices, commercial input use, hired labor, agricultural sales and revenues, nonfarm employment and earnings, and general demographic characteristics. The present study reports findings from the land-market survey along with numerous other interviews with producers, buyers and sellers of land, local authorities, and district and national officials in Maputo and its surrounding peri-urban green zones. Section 1 is introductory while section 2 covers the legal foundation of land tenure and describes the various authorities and agencies responsible for setting and enforcing land policy in the peri-urban zone. Section 3 explains the research design and sampling frame used to select households and landholdings for the study, choice of strata, survey instruments, research questions, and data limitations. Section 4 provides a statistical profile of the household economy while section 5 examines processes of land settlement, land acquisition, types and sources of land dispute, and registration benefits. In section 6, economic and political factors are linked with land prices to explain the determination of "reservation" and "offer" prices of land and to evaluate the influence of market factors and Possible asymmetries in information and bargaining position on land-price perceptions.Land Economics/Use,

Music and Mathematics

Mathematics has forever been