Gridlock signalling pathway fashions the first embryonic artery.

Arteries and veins are morphologically, functionally and molecularly very different, but how this distinction is established during vasculogenesis is unknown. Here we show, by lineage tracking in zebrafish embryos, that angioblast precursors for the trunk artery and vein are spatially mixed in the lateral posterior mesoderm. Progeny of each angioblast, however, are restricted to one of the vessels. This arterial-venous decision is guided by gridlock (grl), an artery-restricted gene that is expressed in the lateral posterior mesoderm. Graded reduction of grl expression, by mutation or morpholino antisense, progressively ablates regions of the artery, and expands contiguous regions of the vein, preceded by an increase in expression of the venous marker EphB4 receptor (ephb4) and diminution of expression of the arterial marker ephrin-B2 (efnb2). grl is downstream of notch, and interference with notch signalling, by blocking Su(H), similarly reduces the artery and increases the vein. Thus, a notch-grl pathway controls assembly of the first embryonic artery, apparently by adjudicating an arterial versus venous cell fate decision.     

关于“阳光体育运动”实施效果的思考

采用文献资料法、访谈法、观察法对阳光体育运动实施过程中存在的问题进行反思,认为实施对象与直接执行者不在场,对象群体目的与决策者目标不一致,决策目标与实施方法、策略不协调,对不同年龄、地域、性别学生的实施要求与手段无差别,无经费支撑等是阳光体育运动难以为继的关键所在。     

Prediction from the One‐Way Error Components Model with AR(1) Disturbances

In this paper we extend the works of Baillie and Baltagi (1999, in Analysis of Panels and Limited Dependent Variables Models, Hsiao C et al. (eds). Cambridge University Press: Cambridge, UK; 255–267) and generalize certain results from the Baltagi and Li (1992, Journal of Forecasting 11 : 561–567) paper accounting for AR(1) errors in the disturbance term. In particular, we derive six predictors for the one‐way error components model, as well as their associated asymptotic mean squared error of multi‐step prediction in the presence of AR(1) errors in the disturbance term. In addition, we also provide both theoretical and simulation evidence as to the relative efficiency of our alternative predictors. The adequacy of the prediction AMSE formula is also investigated by the use of Monte Carlo methods and indicates that the ordinary optimal predictor performs well for various accuracy criteria. Copyright © 2011 John Wiley & Sons, Ltd.     

Genetic mapping with SNP markers in Drosophila.

Map-based positional cloning of Drosophila melanogaster genes is hampered by both the time-consuming, error-prone nature of traditional methods for genetic mapping and the difficulties in aligning the genetic and cytological maps with the genome sequence. The identification of sequence polymorphisms in the Drosophila genome will make it possible to map mutations directly to the genome sequence with high accuracy and resolution. Here we report the identification of 7,223 single-nucleotide polymorphisms (SNPs) and 1,392 insertions/deletions (InDels) in common laboratory strains of Drosophila. These sequence polymorphisms define a map of 787 autosomal marker loci with a resolution of 114 kb. We have established PCR product-length polymorphism (PLP) or restriction fragment-length polymorphism (RFLP) assays for 215 of these markers. We demonstrate the use of this map by delimiting two mutations to intervals of 169 kb and 307 kb, respectively. Using a local high-density SNP map, we also mapped a third mutation to a resolution of approximately 2 kb, sufficient to localize the mutation within a single gene. These methods should accelerate the rate of positional cloning in Drosophila.     

Henderson‐Trending of Macroeconomic Variables and Forecasting Accuracy

Using a structural time‐series model, the forecasting accuracy of a wide range of macroeconomic variables is investigated. Specifically of importance is whether the Henderson moving‐average procedure distorts the underlying time‐series properties of the data for forecasting purposes. Given the weight of attention in the literature to the seasonal adjustment process used by various statistical agencies, this study hopes to address the dearth of literature on ‘trending’ procedures. Forecasts using both the trended and untrended series are generated. The forecasts are then made comparable by ‘detrending’ the trended forecasts, and comparing both series to the realised values. Forecasting accuracy is measured by a suite of common methods, and a test of significance of difference is applied to the respective root mean square errors. It is found that the Henderson procedure does not lead to deterioration in forecasting accuracy in Australian macroeconomic variables on most occasions, though the conclusions are very different between the one‐step‐ahead and multi‐step‐ahead forecasts. Copyright © 2011 John Wiley & Sons, Ltd.     

Riparian vegetation along the middle Snake River, Idaho: zonation, geographical trends, and historical changes

A baseline study was conducted on an 83-km free-flowing reach of the Snake River between Swan Falls Dam and the Idaho-Oregon border. The research had 2 components: (1) field characterization and inventory of existing riparian flora, vegetation, and environment (soils, topography, streamflow), and (2) determination and mapping, using a geographic information system, of historic changes in riparian vegetation based on a time series (1938-39, 1957, 1969, 1987) of aerial photographs. The flora was diverse, with 185 species of vascular plants identified, 63 of which were exotics. Vegetation was structured vertically along the riverbank gradient into lifeform-defined habitat types: emergent, riparian shrub-forb, tree, transitional grass-shrub, and upland. Riverbank seepage, probably of agricultural origin, blurred zonation patterns on some sites and added species to the overall flora. Upstream-downstream differences existed in the physical characteristics and vegetation of river subreaches. Coverage of riparian woodland, island riparian and total riparian vegetation, and area of islands increased since the 1930s, with the greatest changes in the 1969-1987 interval. Possible contributing facts were (1) significant declines in annual minimum flows since the 1950s, (2) decreases in peak flows following the completion of Swan Falls Dam and some upstream dams since the 1920s, (3) introduction and spread of exotic tree species ( Elaeagnus angustifolia and Tamarix spp.) and (4) possible effects of intensive agriculture on river sediment load and soil nutrients. The introduction and proliferation of purple loosestrife ( Lythrum salicaria ) could have considerable future effects on vegetation-channel dynamics in the middle Snake River.     

Characteristics of natal and non-natal kit fox dens in the northern Chihuahuan Desert

We studied kit fox den characteristics of the northern McGregor Range of Fort Bliss Military Reservation, New Mexico, during 1994 to 1995. Twenty radio-collared kit foxes used 132 different dens, including 16 natal dens. Kit fox dens were located primarily in creosote-dominated habitat found in relatively flat, well-drained terrain. Natal dens were virtually indistinguishable from non-natal dens; however, natal den entrances were taller than non-natal den entrances. Entrances found at all dens were oriented more frequently toward the northwest and southwest. Kit foxes used more dens during the breeding (January-February) and pup-rearing season (May-July) than during gestation.     

Ecological comparison of sympatric populations of sand lizards ( Cophosaurus texanus and Callisaurus draconoides )

Sympatric populations of Cophosaurus texanus and Callisaurus draconoides were periodically sampled from March 1973 through April 1974 at Burro Creek, Mohave County, Arizona. Callisaurus were also sampled at Rock Valley, Nye County, Nevada. Sex ratios were skewed in favor of males in the adult Cophosaurus but were equal in both adult populations of Callisaurus. Both species became sexually mature as yearlings. Mean clutch sizes were 3.55 (±0.83) for Cophosaurus, and 4.25 (±1.08) and 5.07 (±1.33) for Callisaurus at Burro Creek and Rock Valley respectively. Evidence of multiple clutches was exhibited by both species. Egg weight/body weight ratios for both species and clutch weight/body weight ratios for Cophosaurus were notably smaller than previously reported. At Burro Creek both species were highly insectivorus, with orthopterans comprising the largest food group of each. Niche overlap for food was high at the ordinal level, but at the familial level it is apparent that Callisaurus probably fed in the more xeric areas of the riparian habitat. No differences were found in the temperature responses of these two lizards. However, minor temporal separations and substantial spatial partitioning were observed. Callisaurus preferred sandy open areas, while Cophosaurus preferred the presence of some rocks and boulders.     

Trapping methods for rangeland insects in burned and unburned sites: a comparison

Different insect trapping methods were compared weekly on recently burned and nearby unburned rangeland in the Great Basin of western Utah. Flight traps (or wing traps) collected the most specimens (total = 4,916 at burned site, 4,384 at unburned site) but represented the fewest species (no more than 11 spp./wk at either site); this method was not recommended because of difficulty in removing specimens from adhesive. Water traps amassed the next largest number of specimens (￣x ± SE/wk = 150.9 ± 75.3 at burned site, 158.0 ± 66.4 at unburned site) and the most species (￣x ± SE/wk = 21.6 ± 6.4 at burned site, 35. 1 ± 4.5 at unburned site). The weekly collections from pitfall traps between the sites were significantly different (P < .05) in number of specimens (￣x ± SE/wk = 8.1 ± 1.5 at burned site, 19.7 ± 4.8 at unburned site) and species (￣x ± SE/wk = 4.7 ± 0.6 at burned site, 9.5 ± 2.0 at unburned site). Malaise traps were the most convenient. Black Malaise traps collected more specimens (￣x ± SE/wk = 99.8 ± 19.4 at burned site, 90.6 ± 16.4 at unburned site) and species (￣x ± SE/wk = 22.9 ± 3.9 at burned site, 19.4 ± 6.5 at unburned site) than white malaise traps (specimens: ￣x ± SE/wk = 72.1 ± 22.4 at burned site, 87.1 ± 31.2 at unburned site; species: ￣x ± SE/ wk = 19.7 ± 6.6 at burned site, 16.4 ± 5.4 at unburned site), although this difference was not significant.