Determinants of cereal diversity in communities and on household farms of the Northern Ethiopian Highlands:

"On farm conservation of crop diversity poses obvious policy challenges in terms of the design of appropriate incentive mechanisms and possible trade-offs between conservation and productivity. This paper compares factors explaining the inter-specific diversity (diversity among species) and infra-specific diversity (diversity among varieties within a species) of cereal crops grown in communities and on individual farms in the northern Ethiopian highlands....If agrobiodiversity conservation is to be seriously considered as a policy option in these communities, applied economics researchers will need to 1) establish the relationship of cereal diversity conservation to private and social welfare, and 2) articulate the relationship between the names of varieties managed by farmers and infra-specific, genetic diversity measured through agro-morphological or molecular analysis. Methodological advance may be required to relate policies to diversity outcomes measured at various geographical scales or levels of aggregation in the same farming system. Specific issues for further social science research include the relationship of seed management practices, seed markets, tenure and soil conservation practices to diversity conservation, and the possible application of bio-economic models to the analysis of species and genetic diversity interactions with farming systems. For policy purposes, it will be important to better understand the particular institutional and social elements that cause communities to behave differently in terms of conservation than the individual household farms of which they are composed, and for some communities to conserve more than others. " Authors' AbstractEthiopia, households, Farms, small, africa, Biological diversity conservation, Communities,

THE DETERMINANTS OF CEREAL CROP DIVERSITY ON FARMS IN THE ETHIOPIAN HIGHLANDS

On farm conservation of crop diversity entails policy challenges, especially when the diversity of crops maintained on farms has both inter-specific (among crops) and infra-specific (within a crop) components. Survey data is used to compare the determinants of inter- and infra-specific diversity on household farms in the highlands of northern Ethiopia. Physical features of the farm, and household characteristics such as livestock assets and the proportion of adults that are men, have large and significant effects on both the diversity among and within cereal crops grown, varying among crops. Demographic aspects such as age of household head and adult education levels affect only infra-specific diversity of cereals. Though there are no apparent trade-offs between policies that would enhance one type of diversity (richness) versus another (evenness), those designed to encourage infra-specific diversity in one cereal crop might have the opposite effect on another crop. Trade-offs between development and diversity in this resource-poor system are not evident. Market-related variables and population density have ambiguous effects. Education positively influences cereal crop diversity. Growing modern varieties of maize or wheat does not detract from the richness or evenness of these cereals on household farms.Crop Production/Industries,

Six Years of ScoX-1 Monitoring with BeppoSAX Wide Field Cameras

We performed a systematic analysis of 54 Wide Field Camera (WFC) observations of ScoX-1 available in the BeppoSAX public archive. Observations span over the six years of BeppoSAX mission lifetime and include 690 hr of data. We searched for shifts and shape changes of the Z pattern in the color-color diagrams. We find that the Z pattern occupies most of the time the same locus in the color-color diagram. There are however a few exceptions, which are discussed in detail.Comment: 4 Pages, 4 figures. To appear in Proc. of the BeppoSAX Symposium: "The Restless High-Energy Universe", E.P.J. van den Heuvel, J.J.M. in 't Zand, and R.A.M.J. Wijers (Eds

Discovery of a 270 Hz X-Ray Burst Oscillation in the X-Ray Dipper 4U 1916-053

We report the discovery of a highly coherent oscillation in a type-I X-ray burst observed from 4U 1916-053 by the Rossi X-ray Timing Explorer (RXTE). The oscillation was most strongly detected approx. 1 s after the burst onset at a frequency of 269.3 Hz, and it increased in frequency over the following 4 seconds of the burst decay to a maximum of around 272 Hz. The total measured drift of 3.58 +/- 0.41 Hz (1 sigma) represents the largest fractional change in frequency (1.32 +/- 0.15 %) yet observed in any burst oscillation. If the asymptotic frequency of the oscillation is interpreted in terms of a decoupled surface burning layer, the implied neutron star spin period is around 3.7 ms. However, the expansion of the burning layer required to explain frequency drift during the burst is around 80 m, substantially larger than expected theoretically (assuming rigid rotation). The oscillation was not present in the persistent emission before the burst, nor in the initial rise. When detected its amplitude was 6-12% (RMS) with a roughly sinusoidal profile. The burst containing the oscillation showed no evidence for photospheric radius expansion, while at least 5 of the other 9 bursts observed from the source by RXTE during 1996 and 1998 did. No comparable oscillations were detected in the other bursts. A pair of kilohertz quasi-periodic oscillations (QPOs) has been previously reported from this source with a mean separation of 348 +/- 12 Hz. 4U 1916-053 is the first example of a source where the burst oscillation frequency is significantly smaller than the frequency separation of the kHz QPOs.Comment: 8 pages, 2 figures, 2 tables; accepted for ApJ Letter

The Changing Demand for Culture: Estimation of Cultural Elasticities

Much past research on the nature of demand for recreation or cultural activities has been either economic models based on unrealistic assumptions about willingness-to-pay or sociological models that fail to provide an in-depth analysis of the forces actually affecting the decision to participate. This paper presents an attempt to combine some of the strengths of the traditional economic and sociological methods, while avoiding some of their weaknesses. The method developed produces an index called a cultural elasticity that quantitatively indicates how rates of participation maw be expected to change when certain economic and sociological characteristics in the population change. A numerical example is provided using a recent Canadian national survey on performing arts audiences. Strengths and limitations in the approach are also identified

Eliashberg's proof of Cerf's theorem

Following a line of reasoning suggested by Eliashberg, we prove Cerf's theorem that any diffeomorphism of the 3-sphere extends over the 4-ball. To this end we develop a moduli-theoretic version of Eliashberg's filling-with-holomorphic-discs method.Comment: 32 page

Central melanopsin projections in the diurnal rodent, Arvicanthis niloticus

The direct effects of photic stimuli on behavior are very different in diurnal and nocturnal species, as light stimulates an increase in activity in the former and a decrease in the latter. Studies of nocturnal mice have implicated a select population of retinal ganglion cells that are intrinsically photosensitive (ipRGCs) in mediation of these acute responses to light. ipRGCs are photosensitive due to the expression of the photopigment melanopsin; these cells use glutamate and pituitary adenylate cyclase-activating polypeptide (PACAP) as neurotransmitters. PACAP is useful for the study of central ipRGC projections because, in the retina, it is found exclusively within melanopsin cells. Little is known about the central projections of ipRGCs in diurnal species. Here, we first characterized these cells in the retina of the diurnal Nile grass rat using immunohistochemistry (IHC). The same basic subtypes of melanopsin cells that have been described in other mammals were present, but nearly 25% of them were displaced, primarily in its superior region. PACAP was present in 87.7% of all melanopsin cells, while 97.4% of PACAP cells contained melanopsin. We then investigated central projections of ipRGCs by examining the distribution of immunoreactive PACAP fibers in intact and enucleated animals. This revealed evidence that these cells project to the suprachiasmatic nucleus, lateral geniculate nucleus (LGN), pretectum, and superior colliculus. This distribution was confirmed with injections of cholera toxin subunit β coupled with Alexa Fluor 488 in one eye and Alexa Fluor 594 in the other, combined with IHC staining of PACAP. These studies also revealed that the ventral and dorsal LGN and the caudal olivary pretectal nucleus receive less innervation from ipRGCs than that reported in nocturnal rodents. Overall, these data suggest that although ipRGCs and their projections are very similar in diurnal and nocturnal rodents, they may not be identical.This study was supported by the National Science Foundation grant (IOS-1051919) to LS and the Danish Biotechnology Center for Cellular Communication (JH)