63,905 research outputs found
Measurement of the ratio of prompt χ c to J / ψ production in pp collisions at √s = 7 TeV
No full textThe prompt production of charmonium χ c and J / ψ states is studied in proton-proton collisions at a centre-of-mass energy of √s = 7 TeV at the Large Hadron Collider. The χ c and J / ψ mesons are identified through their decays χ c → J / ψ γ and J / ψ → μ + μ - using 36 pb - 1 of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for χ c and J / ψ, σ (χ c → J / ψ γ) / σ (J / ψ), is determined as a function of the J / ψ transverse momentum in the range 2 < p T J / ψ < 15 GeV / c. The results are in excellent agreement with next-to-leading order non-relativistic expectations and show a significant discrepancy compared with the colour singlet model prediction at leading order, especially in the low p T J / ψ region
3H-muscimol binding sites within the rat choroid plexus: pharmacological characterization and autoradiographic localization.
No full textBy using combined radioreceptor binding and autoradiographic techniques, we were able to localize the GABA 'A' receptor agonist 3H-muscimol in the rat choroid plexus. Within sections of rat choroid plexus, 3H-muscimol was bound specifically with a KD of 37 nM and a Bmax of 253 pmol/mg tissue. These values are consistent with the labelling of GABA 'A' receptor sites. The autoradiographic studies demonstrated that 3H-muscimol was attached to the epithelium of the choroid plexus. The blood vessels of the plexus did not exhibit specific labelling. Examination of these data suggests the existence of GABAergic mechanisms which control cerebrospinal fluid production or flow
Votes and Violence: Evidence from a Field Experiment in Nigeria
No full textFollowing the wave of democratization during the 1990s, elections are now common in low-income societies. However, these elections are frequently flawed. We investigate the Nigerian general election of 2007, which is to date the largest election held in Africa and one seriously marred by violence. We designed and conducted a nationwide field experiment based on randomized anti-violence grassroots campaigning. We find direct effects on violence outcomes from exploring both subject-surveying and independent data sources. Crucially, we establish that voter intimidation is effective in reducing voter turnout, and that the violence was systematically dissociated from incumbents. We suggest that incumbents have a comparative advantage in alternative strategies, vote buying and ballot fraud. Voter intimidation may be a strategy of the weak analogous to terrorism.Violence, Conflict, Electoral Politics, Political Economy, Randomized Experiment, Field Experiment, Nigeria, West Africa
Distribution and evolution of starspots on the RS CVn binary II Pegasi in 2004
No full textThis work is supported by National Natural Science Foundation of China through grants Nos. 10373023, 10773027 and 11333006, Chinese Academy of Sciences through project KJCX2-YW-T24.We present Doppler images of RS CVn-type binary II Peg based on two data sets obtained in 2004 February and November. In order to improve signal-to-noise ratio and reliability,we apply least-squares deconvolution technique to calculate average profiles from 2032 photospheric absorption lines. Both of the resulting surface images show a wide latitude distribution of starspots. Most spots are concentrated at a high-latitude belt above 60° and a low-latitude belt near equator. The starspots evolved dramatically between two observing runs, which may indicate shorter time-scale evolution in this epoch, especially for low-latitude belt. There is no stable preferred active longitude that can be found in our images. We also find out a possible phenomenon that the intermediate-latitude spot migrated poleward and merged with the high-latitude spot to make it stronger, which may reveal a more complex behaviour of starspots on II Peg. A potential change of orbital ephemeris zero-point was detected. This may imply an orbital period change of II Peg like other active close binaries.Peer reviewe
Cardiac Autonomic Modulation in Preadolescents Following 4 and 8 Weeks of Play-based Summer Activity
No full textPediatric obesity is associated with a decrease in cardiac autonomic modulation and
baroreflex sensitivity. Physical activity increases heart rate variability in adults, yet no
study has elucidated the mode and intensity of exercise for beneficial effects on
cardiac autonomic modulation in children. Objective: The purpose of our study was to
examine the effectiveness of 4 and 8 weeks of supervised, play-based activity on blood
pressure, heart rate variability and baroreflex sensitivity in preadolescents. Methods:
Twenty-two, 8 to 12 year-old children were randomly divided into a 4- and 8-week
activity group and an unsupervised control group (4w n=6, 8w n=6, and C n=10). 4w
and 8w groups performed play-based activities 5 days per week, 4 hours a day while C
group were instructed to maintain a regular summer break with no supervised
intervention. Heart rate variability and baroreflex sensitivity were tested before and
after exercise with a heads-up tilt test. Results: systolic blood pressurewas significantly
lower in all three groups in post conditions (P=0.017, eta2=6.86). Normalized low and
high frequencies reported a significant group-by-time difference in both supine resting
conditions and after heads-up tilt (P=0.043, eta2=0.283 and P=0.05, eta2=0.277,
respectively) and total power in supine position (P=0.038, eta2=0.294) between the
8w, and the 4w and C groups, while baroreflex sensitivity increased by only 3
ms/mmHg in the 8w group. Conclusion: 8 weeks of supervised, play-based physical
activity improved autonomic nervous system activation with favorable changes in
sympathovagal balance in preadolescents during summer break
"Economic Aid to Post-conflict Countries: A Methodological Critique of Collier and Hoeffler"
No full textThis paper retests the analysis of "Aid Policy and Growth in Post-Conflict Societies," by Paul Collier and Anke Hoeffler (October 2002 and forthcoming in European Economic Review). It finds that their data and analysis do not support their conclusions and policy recommendations on the optimal timing and amounts of aid. These conclusions depend on very few observations (13 for the period of peace-onset, 13 for years 4 to 7 when a growth spurt is said to make aid particularly effective, and 8 for the period when aid should taper off); are vulnerable to the same methodological misspecifications identified in the Burnside and Dollar approach on which this analysis is based; and are not grounded in any theoretical formulation about the special relation between aid and growth in post-conflict conditions. Conventional econometric procedures are often not followed; recoding the sample to exclude cases that are not civil wars reduces the effect of aid on growth in post-civil war countries to less than half of what they claim; and the difference with the relationship for "normal" countries becomes negligible (0.26 percentage points), although it depends on identification of the sample. Their claims on the poverty-efficiency of aid are assumed, not analysed. The confidentiality of their policy measure (CPIA) prevented testing the aid-policy relationship.Economic aid Post-conflict Methodology
Comparison of riparian willows and riprap as habitat for fish and invertebrates in the Waikato River
No full textWillows (Salix spp.) are an abundant alien tree and have been the mainstay of river bank protection throughout New Zealand. Riprap is another method of bank stabilisation consisting of rocks used to amour shorelines to protect against erosion. There is a trend for increasing use of riprap to replace willow along the banks of large rivers in New Zealand, but there is limited information on the ecological roles of these different bank types to support management. The objectives of this research were to determine the effects of different bank habitats on nearshore fish and invertebrate communities in the Waikato River as it passes through Hamilton city. The study involves three sites situated along the river. Each site has four bank types consisting of willow, riprap, a mixture of willow and riprap, and beach. Invertebrate sampling was carried out on three occasions to assess if there was a seasonal effect on community composition. Fish were sampled bimonthly determine differences in community composition. Assessment of fish populations was carried out with using boat electrofishing, Gee minnow trapping and spotlighting, while invertebrate populations were sampled by kick netting. Few significant differences were detected in invertebrate diversity between willow, riprap and willow/riprap habitats. However, community composition based on relative abundance was different among contrasting habitats in most seasons and Pielou’s evenness was greater for the more homogenous beach and riprap habitats. Riprap had consistently high alpha diversity but had lower species accumulation on two out of three dates suggesting there was a limited pool of taxa colonising the riprap compared to other habitats. Pairwise dissimilarity coefficients and PERMANOVA comparisons indicated that, although low in alpha diversity, beach habitats contributed significantly to macroinvertebrate beta diversity, and that willow and riprap habitats also supported different combinations of taxa due to different physical conditions. The combination of beach and willow habitats gave the highest gamma diversity. Willow habitats supported the highest number of both introduced and native fish, mainly reflecting abundances of common smelt, likely due to provision of cover, complex aquatic habitat, and riparian vegetation supplying detritus and invertebrate food resources. Riprap habitats supported the highest number of common bully. Common bully were also significantly larger in this habitat. Variations in water temperature, amount of shade, and river levels were possible factors contributing to temporal influences on biological patterns. The findings of this study indicate that, if all banks habitats in Hamilton City were composed of a single type, invertebrate biodiversity would be reduced. While the combination of beach and willow habitats may sustain high diversity for invertebrates and fish, the novel habitat provided by riprap may also favour some native fish and invertebrates over others. Therefore, a balance of different bank habitat types would perhaps be best to sustain present-day biodiversity levels in near shore macroinvertebrate and fish communities
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