Harvesting an invasive bivalve in a large natural lake: species recovery and impacts on native benthic macroinvertebrate community structure in Lake Tahoe,USA

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Identification of a juvenile hormone-like compound in a crustacean

Juvenile hormone (JH) has central roles in the regulation of insect development and reproduction but has not previously been identified in other arthropod classes. The hemolymph of a crustacean, Libinia emarginata (Leach), has now been analyzed for JH-like compounds. Samples contained 0.003 to 0.030 nanogram of JH III per milliliter and 10 to 50 nanograms of methyl farnesoate per milliliter; methyl farnesoate is a compound structurally related to JH III that has JH bioactivity. Several tissues were examined for synthesis and secretion of JH-like compounds. Of these tissues, only the mandibular organs produced and secreted JH III and methyl farnesoate. However, microchemical analysis revealed that this JH III was racemic, and thus likely an artifactual oxidation product of methyl farnesoate. Secretion of methyl farnesoate was related to reproduction in females, with the highest rates observed in Libinia near the end of the ovarian cycle when oocyte growth and vitellogenesis are greatest. These results indicate that JH-like compounds such as methyl farnesoate have regulatory roles in crustaceans.     

Sum rules and interlayer conductivity of high-Tc cuprates

Analysis of the interlayer infrared conductivity of cuprate high-transition temperature superconductors reveals an anomalously large energy scale extending up to midinfrared frequencies that can be attributed to formation of the superconducting condensate. This unusual effect is observed in a va- riety of materials, including Tl2Ba2CuO6+x, La2-xSrxCuO4, and YBa2Cu3O6.6, which show an incoherent interlayer response in the normal state. Midinfrared range condensation was examined in the context of sum rules that can be formulated for the complex conductivity. One possible interpretation of these experiments is in terms of a kinetic energy change associated with the superconducting transition.     

Calcium current and activation of contraction in ventricular myocardial fibers

In thin bundles of dog ventricular myocardium, a slow inward current (distinct from the sodium inward current) could be recorded under voltageclamp conditions. This inward current was influenced by changes in external calcium concentration, but it was not dependent on external sodium concentration. Therefore, this current which contributes an appreciable amount of charge transfer during the plateau of the action potential, is carried by calcium ions. In sodium-free solution, the flow of calcium ions into the fiber is directly related to activation of contraction. In sodium-containing solution, however, calcium inward current serves primarily to fill up some intracellular stores from which calcium can be released by moderate depolarization.     

Sediment budget for subalpine watersheds,Lake Tahoe,California, USA

Pinpointing erosional ‘hot spots’ or sediment source areas within a watershed can be difficult because of the highly non-linear and episodic nature of effective runoff and sediment transport. Continuous monitoring of stream networks can provide insight into sediment source areas not possible from routine sampling by capturing episodic events and integrating entire storm events. This paper presents the results of a three-year study of spring snowmelt runoff in watersheds of Lake Tahoe, California, USA, using a network of nine nephelometric turbidometers. We estimate that montane badlands, comprising 1.2% of the Ward Creek watershed (25 km²), contributed 10–39% of snowmelt-derived suspended sediment load. The badlands are comprised of poorly-vegetated and deeply-incised gullies formed in parent material of Miocene volcanic mudflow breccia. The larger (29.5 km²) Blackwood Creek watershed also showed high relative erosion rates from volcanic terrain. Tributaries draining forested granitic and metasedimentary headwater regions had minimal sediment loads. Monitoring networks indicated that temporary main channel storage regulated release of fine sediment eroded from steep headwater slopes. This lag between erosion and delivery may lead to underestimation of gully erosion contribution to sediment budgets.     

Initial formation of soil organic matter from grass residues in a long-term experiment

Summary The formation of soil organic matter from grass residues was studied using samples of a long-term experiment (34 years) on humus and soil formation at Rostock, Germany (Hu 3), by elemental analyses (C and N) and pyrolysis-field ionization mass spectrometry of grass residues, humus-free loamy marl, mixtures of this loamy marl with grass roots, and whole soil samples from the 2nd, 7th, 13th, 19th, 25th, 29th, and 34th year of the experiment. The pyrolysis-field ionization mass spectra of the two grass species Phleum pratense and Lolium multiflorum were similar insofar as signals characteristic of lignin dimers and phytosterols dominated at higher masses and for mono-and polysaccharides at lower masses. The most prominent differences between overand underground plant constituents were indicated by higher relative abundances of lignin dimers in the stems and leaves and of sugars and suberin-derived phytosterols in the roots. In the investigation of the influence of mineral to organic matter ratios, comparatively weak effects of the inorganic matrix were obtained: firstly, in the lower mass range (m/z<250), secondly, for organic matter concentrations between 1.0% and 2.0%, and thirdly, for certain classes of compounds such as phenols, alkanes/alkenes, N heterocycles and mono-and polysaccharides. The qualitative differences in the molecular composition of soil organic matter were clearly attributed to its rapid increase during the first 7 years of the experiment and largely originated from a relative enrichment of lignin dimers. Then, in the period of steady-state soil organic matter levels, dynamic changes were indicated by slight enrichments of mono-and polysaccharides, alkanes/alkenes, fatty acids, N heterocycles, and fluctuating data for phenols/lignin monomers, lignin dimers, and the sum of N compounds. Alkylaromatics showed a steep increase between the 13th and 19th years and remained then on a high level.     

Jupiter cloud composition, stratification, convection, and wave motion: a view from new horizons

Several observations of Jupiter's atmosphere made by instruments on the New Horizons spacecraft have implications for the stability and dynamics of Jupiter's weather layer. Mesoscale waves, first seen by Voyager, have been observed at a spatial resolution of 11 to 45 kilometers. These waves have a 300-kilometer wavelength and phase velocities greater than the local zonal flow by 100 meters per second, much higher than predicted by models. Additionally, infrared spectral measurements over five successive Jupiter rotations at spatial resolutions of 200 to 140 kilometers have shown the development of transient ammonia ice clouds (lifetimes of 40 hours or less) in regions of strong atmospheric upwelling. Both of these phenomena serve as probes of atmospheric dynamics below the visible cloud tops.     

The surveillance of plant hygiene in the slaughtering process

Basing on inspections of slaughterhouses it was tried to judge the effectiveness of the hygiene supervision implemented by the legislation. The organization of the control, the technological process including abattoir constructions and operations, the general hygienic aspects with special regard to cleaning and disinfection were registered. It is clearly demonstrated by grave examples (eg. wrong organization, insufficient employment of staff, incomplete knowledge, illegal practices) that nowadays in spite of a few exceptions, the supervision of hygiene in abattoirs is fragmentary. Paying attention to the conceptions of EEC committees dealing already with systematic controls, it would be well done to establish already known systems at once in the plants. According to the meat hygiene regulations exclusively official veterinarians are competent for this field of activities. These have to take the actual scientific knowledge into consideration.