Open-incubation, diffusion methods for measuring solute reaction rates in sediments

Sedimentary solute distributions and fluxes are determined in part by the kinetics of production/consumption reactions in a deposit. It is possible to estimate rates and investigate kinetic relations in undisturbed or manipulated sediments by documenting build-up or depletion patterns of solutes allowed to diffuse either between relatively thin sections of sediment and a well-stirred water reservoir (plug incubation); or through a large section of sediment without an overlying reservoir (whole-core incubation). The time-dependent concentrations in the sediment in both cases depend on reaction rates, kinetics, diffusion coefficients, and geometric scaling of the sediment and contacting reservoir. Major advantages of the plug incubation method are that interactions between classes of sedimentary reactions can be examined by manipulating the composition of the stirred water reservoir, and kinetic relations, such as reaction order, can be inferred from comparisons of reaction rate with steady-state concentrations of pore water solutes. The water reservoir size and sediment thickness can be altered to allow rapid estimates of reaction rates at near steady-state or to examine nonsteady-state behavior. Nonsteady-state models are always required for the whole-core incubation method. This latter method has the advantages that it is less labor-intensive than many other rate measurement methods and the incubations can be performed in situ. Experimental comparisons between open-incubation and more traditional closed-incubation estimates of reaction rates show good agreement for solutes such as NH4+, SO4–, HPO4– and I–. In some cases, such as Mn++, Fe++, and HPO4– production, where major back-reactions with sediment occur, open-incubations without substantial build-up of solutes may provide the most accurate method for estimating production rates. In principle, the open incubation methods described in this paper can be used for any diffusable species

Rate dependence of hysteresis in one-dimensional phase transitions

Two models for solid-solid phase transition in one-dimension are examined. Thermal dissipation and a rate-type viscosity are added to a stress with strain gradient. Numerical examinations of both models reveal similar results, in particular, stress-strain hysteresis, which is a commonly observed phenomena, and stability of single-phase boundary solutions

EGO-1 is related to RNA-directed RNA polymerase and functions in germ-line development and RNA interference in C. elegans

AbstractBackground: Cell-fate determination requires that cells choose between alternative developmental pathways. For example, germ cells in the nematode worm Caenorhabditis elegans choose between mitotic and meiotic division, and between oogenesis and spermatogenesis. Germ-line mitosis depends on a somatic signal that is mediated by a Notch-type signaling pathway. The ego-1 gene was originally identified on the basis of genetic interactions with the receptor in this pathway and was also shown to be required for oogenesis. Here, we provide more insight into the role of ego-1 in germ-line development.Results: We have determined the ego-1 gene structure and the molecular basis of ego-1 alleles. Putative ego-1 null mutants had multiple, previously unreported defects in germ-line development. The ego-1 transcript was found predominantly in the germ line. The predicted EGO-1 protein was found to be related to the tomato RNA-directed RNA polymerase (RdRP) and to Neurospora crassa QDE-1, two proteins implicated in post-transcriptional gene silencing (PTGS). For a number of germ-line-expressed genes, ego-1 mutants were resistant to a form of PTGS called RNA interference.Conclusions: The ego-1 gene is the first example of a gene encoding an RdRP-related protein with an essential developmental function. The ego-1 gene is also required for a robust response to RNA interference by certain genes. Hence, a protein required for germ-line development in C. elegans may be a component of the RNA interference/PTGS machinery

Scientific questions for the exploration of the terrestrial planets and Jupiter - Advanced planetary missions technology program Progress report

Scientific questions and experimental design for planetary exploration of Jupiter, Mars, Mercury, and Venu

Isolation and Characterisation of Genes Encoding Malate Synthesis and Transport Determinants in the Aluminum-Tolerant Australian Weeping-Grass (\u3cem\u3eMicrolaena Stipoides\u3c/em\u3e)

Acid soils cover some 40% of the Earth’s arable land where they represent a major limitation to plant production. Plant growth on acid soils is primarily limited due to aluminium (Al) solubilized by acidity into toxic Al3+ cations which will inhibit root growth resulting in poor uptake of water and nutrients. Many important pasture species lack sufficient Al tolerance within their germplasm to allow effective breeding for this character

ACVIM consensus statement on the treatment of immune-mediated hemolytic anemia in dogs

Immune‐mediated hemolytic anemia (IMHA) causes severe anemia in dogs and is associated with considerable morbidity and mortality. Treatment with various immunosuppressive and antithrombotic drugs has been described anecdotally and in previous studies, but little consensus exists among veterinarians as to the optimal regimen to employ and maintain after diagnosis of the disease. To address this inconsistency and provide evidence‐based guidelines for treatment of IMHA in dogs, we identified and extracted data from studies published in the veterinary literature. We developed a novel tool for evaluation of evidence quality, using it to assess study design, diagnostic criteria, explanation of treatment regimens, and validity of statistical methods. In combination with our clinical experience and comparable guidelines for humans afflicted with autoimmune hemolytic anemia, we used the conclusions of this process to make a set of clinical recommendations regarding treatment of IMHA in dogs, which we refined subsequently by conducting several iterations of Delphi review. Additionally, we considered emerging treatments for IMHA in dogs and highlighted areas deserving of future research. Comments were solicited from several professional bodies to maximize clinical applicability before the recommendations were submitted for publication. The resulting document is intended to provide clinical guidelines for management of IMHA in dogs. These guidelines should be implemented pragmatically, with consideration of animal, owner, and veterinary factors that may vary among cases

Isolation and Characterisation of Genes Encoding Ice Recrystallisation Inhibition Proteins (IRIPs) in the Cryophilic Antarctic Hair-Grass (\u3ci\u3eDeschampsia Antarctica\u3c/i\u3e) and the Temperate Perennial Ryegrass (\u3ci\u3eLolium Perenne\u3c/i\u3e)

Antarctic hairgrass (D. antarctica Desv.), the only grass species indigenous to Antarctica, has a well developed tolerance of freezing, strongly induced by cold-acclimation. In response to low temperatures D. antarctica exhibits recrystallisation inhibition (RI) activity, localised to the apoplasm, that prevents further growth of ice crystals following freezing