Effets de l'irradiation sur le métabolisme des acides nucléiques et de leurs dérivés acidosolubles chez le rat

Summary In the rat, X-irradiation leads to a decrease of the net RNA and DNA content of the spleen, without, however, increasing the low molecular weight nucleic acid derivatives in the acid-soluble fractions of the same tissue. It is suggested that an alteration of the cell membranes could account for the apparent elimination of these nucleic acid degradation products which should normally appear in the acid-soluble fraction.     

Spatially resolved electronic structure inside and outside the vortex cores of a high-temperature superconductor

Puzzling aspects of high-transition-temperature (high-Tc) superconductors include the prevalence of magnetism in the normal state and the persistence of superconductivity in high magnetic fields. Superconductivity and magnetism generally are thought to be incompatible, based on what is known about conventional superconductors. Recent results, however, indicate that antiferromagnetism can appear in the superconducting state of a high-Tc superconductor in the presence of an applied magnetic field. Magnetic fields penetrate a superconductor in the form of quantized flux lines, each of which represents a vortex of supercurrents. Superconductivity is suppressed in the core of the vortex and it has been suggested that antiferromagnetism might develop there. Here we report the results of a high-field nuclear-magnetic-resonance (NMR) imaging experiment in which we spatially resolve the electronic structure of near-optimally doped YBa2Cu3O7-delta inside and outside vortex cores. Outside the cores, we find strong antiferromagnetic fluctuations, whereas inside we detect electronic states that are rather different from those found in conventional superconductors.     

Increase in superoxide dismutase activity induced by thyroid hormones in the brains of neonate and adult rats

Summary The activity of cytoplasmic superoxide dismutase (SOD) in the liver was about twice as high in adult rats as it was in neonates. In the brain and in the interscapular brown adipose tissue (IBAT), SOD activity was not changed during postnatal development, although it was slightly higher in the brain than in the IBAT (p>0.1). Thyroid hormones produced an increase in SOD activity in the brain of newborn rats, as well as in those animals 30 and 60 days old. The same quantity of hormones did not produce any significant changes in the liver or in the IBAT.     

Evidence of diurnal fluctuation of sensitivity to noradrenaline in the rat — the role of the thyroid

Summary The capacity for heat production, under the influence of the same amount of noradrenaline, in the rat was significantly higher in the evening (20.00 h) than in the morning (07.00 h). Thyroidectomy produces not only a lower level of heat production, but also a complete disappearance of the differences between the morning and the evening experiments.     

Xenopsin stimulates exocrine pancreatic secretion in the dog

Summary The octapeptide xenopsin, previously isolated from amphibian skin, stimulates exocrine pancreatic secretion of bicarbonate and protein in conscious dogs and increases the volume of secretion. This effect is shown in the dose range of 1.25 up to 160 pmoles kg^–1min^–1 The high potency of this peptide is suggestive of a possible physiological role of xenopsin in mammals.This work was supported by the Deutsche Forschungsgemeinschaft Fe 127/4.     

Influences of synthesis methods and modifier addition on the properties of Ni-based catalysts supported on reticulated ceramic foams

A method of synthesizing Ni-based catalysts supported on α-Al₂O₃-based foams was developed. The foams were impregnated with aqueous solutions of metal chlorides under an air atmosphere using an aerosol route. Separate procedures involved calcination to form oxides and drying to obtain chlorides on the foam surface. The synthesized samples were subsequently reduced with hydrogen. With respect to the Ni/Al₂O₃ catalysts, the chloride reduction route enabled the formation of a Ni coating without agglomerates or cracks. Further research included catalyst modification by the addition of Pd, Cu, and Fe. The influences of the additives on the degree of reduction and on the low-temperature reduction effectiveness (533 and 633 K) were examined and compared for the catalysts obtained from oxides and chlorides. Greater degrees of reduction were achieved with chlorides, whereas Pd was the most effective modifier among those investigated. The reduction process was nearly complete at 533 K in the sample that contained 0.1wt% Pd. A lower reduction temperature was utilized, and the calcination step was avoided, which may enhance the economical and technological aspects of the developed catalyst production method.     

Optical nano-imaging of gate-tunable graphene plasmons

The ability to manipulate optical fields and the energy flow of light is central to modern information and communication technologies, as well as quantum information processing schemes. However, because photons do not possess charge, a way of controlling them efficiently by electrical means has so far proved elusive. A promising way to achieve electric control of light could be through plasmon polaritons—coupled excitations of photons and charge carriers—in graphene. In this two-dimensional sheet of carbon atoms, it is expected that plasmon polaritons and their associated optical fields can readily be tuned electrically by varying the graphene carrier density. Although evidence of optical graphene plasmon resonances has recently been obtained spectroscopically, no experiments so far have directly resolved propagating plasmons in real space. Here we launch and detect propagating optical plasmons in tapered graphene nanostructures using near-field scattering microscopy with infrared excitation light. We provide real-space images of plasmon fields, and find that the extracted plasmon wavelength is very short—more than 40 times smaller than the wavelength of illumination. We exploit this strong optical field confinement to turn a graphene nanostructure into a tunable resonant plasmonic cavity with extremely small mode volume. The cavity resonance is controlled in situ by gating the graphene, and in particular, complete switching on and off of the plasmon modes is demonstrated, thus paving the way towards graphene-based optical transistors. This successful alliance between nanoelectronics and nano-optics enables the development of active subwavelength-scale optics and a plethora of nano-optoelectronic devices and functionalities, such as tunable metamaterials, nanoscale optical processing, and strongly enhanced light–matter interactions for quantum devices and biosensing applications.     

Application of species-richness estimators for the assessment of earthworm diversity

This paper includes the current knowledge of earthworm distribution and richness in the central part of the Balkans, in the state of Serbia. The work is based on data obtained from fieldwork in the western part of Serbia. The aim is to follow a methodological and theoretical framework for the application of species-richness estimators in earthworm biodiversity research. We have evaluated the performance of various estimation techniques to assess the different species-richness estimators in EstimateS. The following estimators (EstimateS 8.2) were used to extrapolate species richness beyond our own data: ACE, ICE, Chao 1, Chao 2, Jackknife 1, Jackknife 2, Bootstrap, and Michaelis–Menten richness estimator. The Chao 2 and Jackknife 2 richness estimators were considered most appropriate to predict the number of earthworm species and can serve to provide a quantitative basis for assessing long-term changes in species richness.