Scarred limpets at hydrothermal vents: evidence of predation by deep-sea whelks

The chaotic physical and chemical environment at deep-sea hydrothermal vents has been associated with an ecosystem with few predators, arguably allowing the habitat to provide refuge for vulnerable species. The dominance of endemic limpets with thin, open-coiled shells at north Pacific vents may support this view. To test their vulnerability to predation, the incidence of healed repair scars, which are argued to reflect non-lethal encounters with predators, were examined on the shells of over 5,800 vent limpets of Lepetodrilus fucensis McLean (1988) that were collected from 13 to 18 August 1996. Three vent fields on the Juan de Fuca Ridge at ca. 2,200 m depth were sampled, two within 70 m of 47 degrees 56.87'N 129 degrees 05.91'W, and one at 47 degrees 57.85'N 129 degrees 05.15'W with the conspicuous potential limpet predators, the zoarcid fish Pachycara gymninium Anderson and Peden (1988), the galatheid crab Munidopsis alvisca Williams (1988), and the buccinid snail Buccinum thermophilum Harasewych and Kantor (2002). Limpets from the predator-rich vent were most often scarred, a significant difference created by the high incidence of scars on small (

The Bonds of Brotherhood: New Evidence of Sino-North Korean Exchanges, 1950-1954

Drawing on recently declassified documents from the archive of the Foreign Ministry of the People’s Republic of China (PRC), this article looks at China’s relationship with North Korea during and immediately after the Korean War. Although previous scholarship has touched on PRC–North Korean military ties during the war, this article is the first in-depth analysis of issues that are less well understood, notably China’s efforts to cope with a huge influx of refugees from North Korea, the PRC’s economic assistance during the war and in the early postwar reconstruction, and Chinese educational and ideological support for North Korean professionals and party cadres. The article shows that the extensive military coordination between Beijing and Pyongyang was only one way in which the war brought North Korea and the PRC into a closer relationship

Anterior thalmic lesions stop immediate early gene activation in selective laminae of the retrosplenial cortex: evidence of covert pathology in rats

Lesions involving the anterior thalamic nuclei stopped immediate early gene (IEG) activity in specific regions of the rat retrosplenial cortex, even though there were no apparent cytoarchitectonic changes. Discrete anterior thalamic lesions were made either by excitotoxin (Experiment 1) or radiofrequency (Experiment 2) and, following recovery, the rats foraged in a radial-arm maze in a novel room. Measurements made 6-12 weeks postsurgery showed that, in comparison with surgical controls, the thalamic lesions produced the same, selective patterns of Fos changes irrespective of method. Granular (caudal granular cortex and rostral granular cortex), but not dysgranular (dysgranular cortex), retrosplenial cortex showed a striking loss of Fos-positive cells. While a loss of between 79 and 89% of Fos-positive cells was found in the superficial laminae, the deeper layers appeared normal. In Experiments 3 and 4, rats 9-10 months postsurgery were placed in an activity box for 30 min. Anterior thalamic lesions (Experiment 3) led to a pronounced IEG decrease of both Fos and zif268 throughout the retrosplenial cortex that now included the dysgranular area. These IEG losses were found even though the same regions appeared normal using standard histological techniques. Lesions of the postrhinal cortex (Experiment 4) did not bring about a loss of retrosplenial IEG activity even though this region is also reciprocally connected with the retrosplenial cortex. This selective effect of anterior thalamic damage upon retrosplenial activity may both amplify the disruptive effects of anterior thalamic lesions and help to explain the posterior cingulate hypoactivity found in Alzheimer's disease.

No evidence of endothelial dysfunction in patients with Alzheimer's disease

In view of accumulating evidence of vascular pathology in Alzheimer's disease (AD), we tested the hypothesis that AD patients have impaired endothelial function. This was assessed using the technique of strain-gauge venous occlusion plethysmography, which measures forearm blood flow (FBF). Intra-arterial (brachial) infusion of acetylcholine (ACh) and sodium nitroprusside (SNP) was used to assess local endothelial dependent and independent responses, respectively. There was no difference in the basal FBF of patients and controls. ACh and SNP caused dose-related increases in FBF from baseline, but no difference was recorded between the AD and control group. This study provides no evidence of endothelial dysfunction in the systemic circulation of patients with AD.

Flare X-ray Observations of AB Doradus: Evidence of Stellar Coronal Opacity

X-ray spectra of the late-type star AB Dor obtained with the XMM-Newton satellite are analyzed. AB Dor was particularly active during the observations. An emission measure reconstruction technique is employed to analyze flare and quiescent spectra, with emphasis on the Fe XVII 15 - 17 angstrom wavelength region. The Fe XVII 16.78 angstrom/ 15.01 angstrom line ratio increases significantly in the hotter flare plasma. This change in the ratio is opposite to the theoretical predictions and is attributed to the scattering of 15.01 angstrom line photons from the line of sight. The escape probability technique indicates an optical depth of approximate to 0.4 for the 15.01 angstrom line. During the flare, the electron density is 4.4(-1.6)(+2.7) x 10(10) cm(-3), and the fractional Fe abundance is 0.5 +/- 0.1 of the solar photospheric value Using these parameters, a path length of approximate to 8000 km is derived. There is no evidence of opacity in the quiescent X-ray spectrum of the star.

Observational evidence of gentle chromospheric evaporation during the impulsive phase of a solar flare

Observational evidence of gentle chromospheric evaporation during the impulsive phase of a C9.1 solar flare is presented using data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager and the Coronal Diagnostic Spectrometer on board the Solar and Heliospheric Observatory. Until now, evidence of gentle evaporation has often been reported during the decay phase of solar flares, where thermal conduction is thought to be the driving mechanism. Here we show that the chromospheric response to a low flux of nonthermal electrons (>= 5 cm(-2) s(-1)) results in plasma upflows of 13 +/- 16, 16 +/- 18, and 110 +/- 58 km s(-1) in the cool He I and O V emission lines and the 8 MK Fe XIX line, respectively. These findings, in conjunction with other recently reported work, now confirm that the dynamic response of the solar atmosphere is sensitively dependent on the flux of incident electrons.

Macroscopic evidence of soliton formation in multiterawatt laser-plasma interaction

A novel physical phenomenon has been observed following the interaction of an intense (10(19) W/cm(2)) laser pulse with an underdense plasma. Long-lived, macroscopic bubblelike structures have been detected through the deflection that the associated electric charge separation causes in a proton probe beam. These structures are interpreted as the remnants of a cloud of relativistic solitons generated in the plasma by the ultraintense laser pulse. This interpretation is supported by an analytical study of the soliton cloud evolution, by particle-in-cell simulations, and by a reconstruction of the proton-beam deflection.