Method of fabricating an article with cavities

An article having a cavity with a thin bottom wall is provided by assembling a thin sheet, for example, a metal sheet, adjacent to the surface of a member having one or more apertures. A bonding adhesive is interposed between the thin sheet and the subadjacent member, and the thin sheet is subjected to a high fluid pressure. In order to prevent the differential pressure from being exerted against the thin sheet, the aperture is filled with a plug of solid material having a linear coefficient of thermal expansion higher than that of the member. When the assembly is subjected to pressure, the material is heated to a temperature such that its expansion exerts a pressure against the thin sheet thus reducing the differential pressure

Timescales for the development of methanogenesis and free gas layers in recently-deposited sediments of Arkona Basin (Baltic Sea)

Arkona Basin (southwestern Baltic Sea) is a seasonally-hypoxic basin characterized by the presence of free methane gas in its youngest organic-rich muddy stratum. Through the use of reactive transport models, this study tracks the development of the methane geochemistry in Arkona Basin as this muddy sediment became deposited during the last 8 kyr. Four cores are modeled each pertaining to a unique geochemical scenario according to their respective contemporary geochemical profiles. Ultimately the thickness of the muddy sediment and the flux of particulate organic carbon are crucial in determining the advent of both methanogenesis and free methane gas, the timescales over which methanogenesis takes over as a dominant reaction pathway for organic matter degradation, and the timescales required for free methane gas to form

Will the U.S. productivity resurgence continue?

U.S. productivity growth has accelerated in recent years, despite a series of negative economic shocks. An analysis of the sources of this growth over the 1995-2003 period suggests that the production and use of information technology account for a large share of the gains. The authors project that during the next decade, private sector productivity growth will continue at a rate of 2.6 percent per year, a significant increase from their 2002 projection of 2.2 percent growth.Productivity ; Information technology

Projecting productivity growth: lessons from the U.S. growth resurgence

Following the 1995-2000 period of more rapid output growth and lower inflation in the United States, economists have strenuously debated whether improvements in economic performance can be sustained. The recession that began in March 2001 intensified the debate, and the economic impacts of the events of September 11 have yet to be fully understood. Both factors add to the considerable uncertainties about future growth that currently face decision makers in both the public and private sectors. ; In this article, the authors analyze the sources of U.S. labor productivity growth in the post-1995 period and present projections for both output and labor productivity growth for the next decade. Despite the 2001 downward revisions to U.S. gross domestic product and software investment, the authors show that information technology (IT) played a substantial role in the U.S. productivity revival. The article then outlines a methodology for projecting trend output and productivity growth. The base-case projection puts the rate of trend productivity growth at 2.21 percent per year over the next decade with a range of 1.33 to 2.92 percent, reflecting fundamental uncertainties about the rate of technological progress in IT-production and investment patterns. The central projection is only slightly below the average growth rate of 2.36 percent during the 1995-2000 period.Productivity ; Technology ; Economic development

Infection of Soybean and Pea Nodules by \u3cem\u3eRhizobium\u3c/em\u3e spp. Purine Auxotrophs in the Presence of 5-aminoimidazole-4-Carboxamide Riboside

Purine auxotrophs of various Rhizobium species are symbiotically defective, usually unable to initiate or complete the infection process. Earlier studies demonstrated that, in the Rhizobium etli-bean symbiosis, infection by purine auxotrophs is partially restored by supplementation of the plant medium with 5-amino-imidazole-4-carboxamide (AICA) riboside, the unphosphorylated form of the purine biosynthetic intermediate AICAR. The addition of purine to the root environment does not have this effect. In this study, purine auxotrophs of Rhizobium fredii HH303 and Rhizobium leguminosarum 128C56 (bv. viciae) were examined. Nutritional and genetic characterization indicated that each mutant was blocked in purine biosynthesis prior to the production of AICAR. R. fredii HH303 and R. leguminosarum 128C56 appeared to be deficient in AICA riboside transport and/or conversion into AICAR, and the auxotrophs derived from them grew very poorly with AICA riboside as a purine source. All of the auxotrophs elicited poorly developed, uninfected nodules on their appropriate hosts. On peas, addition of AICA riboside or purine to the root environment led to enhanced nodulation; however, infection threads were observed only in the presence of AICA riboside. On soybeans, only AICA riboside was effective in enhancing nodulation and promoting infection. Although AICA riboside supplementation of the auxotrophs led to infection thread development on both hosts, the numbers of bacteria recovered from the nodules were still 2 or more orders of magnitude lower than in fully developed nodules populated by wild-type bacteria. The ability to AICA riboside to promote infection by purine auxotrophs, despite serving as a very poor purine source for these strains, supports the hypothesis that AICAR plays a role in infection other than merely promoting bacterial growth