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

Studies of surface two-dimensional photonic band-gap structures

Two-dimensional (2D) surface photonic band-gap (SPBG) structures can be obtained by providing a shallow corrugation of the inner surface of a waveguide wall. It can be used as a distributed mirror, a cavity, or a filter in integrated optics or microwave electronics. These structures can also be an alternative to conventional 2D PBG or 1D Bragg structures. In this article, we present the results of theoretical and experimental studies of 2D SPBG structures. Data obtained from experiments are compared with theoretical results and good agreement between theory and experiment is demonstrated. Comparison of a coaxial 2D SPBG structure with a conventional 1D Bragg structure is also presented

Comparing Small-Group and Individual Behavior in Lottery-Choice Experiments

Lottery-choice experiments are conducted to compare risk preferences revealed by three-person groups versus isolated individuals. A lottery-choice experiment consists of a menu of paired lottery choices structured so that the crossover point from a low-risk to a high-risk lottery can be used to infer the degree of risk aversion. A between-subjects experiment of group versus individual lottery-choice decisions reveal that there is not a significant difference in the average crossover point, but lottery choices are affected by a significant interaction between subject composition (individual or group) and lottery winning percentage. Also, a three-phased individual-group-individual sequenced experiment reveals that the count of safe lotteries chosen by groups is, on average, significantly greater than the mean of the individual members. Finally, making a phase-two group decision has a significant impact on subsequent phase-three individual decisions relative to the initial phase-one (individual) decisions.lab experiments, risk preferences, group decisions

Comparing Small-Group and Individual Behavior in Lottery-Choice Experiments

Lottery-choice experiments are conducted to compare risk preferences revealed by three-person groups versus isolated individuals. A lottery-choice experiment consists of a menu of paired lottery choices structured so that the crossover point from a low-risk to a high-risk lottery can be used to infer the degree of risk aversion. A between-subjects experiment of group versus individual lottery-choice decisions reveal that there is not a significant difference in the average crossover point, but lottery choices are affected by a significant interaction between subject composition (individual or group) and lottery winning percentage. Also, a three-phased individual-group-individual sequenced experiment reveals that the count of safe lotteries chosen by groups is, on average, significantly greater than the mean of the individual members. Finally, making a phase-two group decision has a significant impact on subsequent phase-three individual decisions relative to the initial phase-one (individual) decisions.lab experiments, risk preferences, group decisions

Theory and simulations of a gyrotron backward wave oscillator using a helical interaction waveguide

A gyrotron backward wave oscillator (gyro-BWO) with a helically corrugated interaction waveguide demonstrated its potential as a powerful microwave source with high efficiency and a wide frequency tuning range. This letter presents the theory describing the dispersion properties of such a waveguide and the linear beam-wave interaction. Numerical simulation results using the PIC code MAGIC were found to be in excellent agreement with the output measured from a gyro-BWO experiment

The Effects of Orbital Motion on LISA Time Delay Interferometry

In an effort to eliminate laser phase noise in laser interferometer spaceborne gravitational wave detectors, several combinations of signals have been found that allow the laser noise to be canceled out while gravitational wave signals remain. This process is called time delay interferometry (TDI). In the papers that defined the TDI variables, their performance was evaluated in the limit that the gravitational wave detector is fixed in space. However, the performance depends on certain symmetries in the armlengths that are available if the detector is fixed in space, but that will be broken in the actual rotating and flexing configuration produced by the LISA orbits. In this paper we investigate the performance of these TDI variables for the real LISA orbits. First, addressing the effects of rotation, we verify Daniel Shaddock's result that the Sagnac variables will not cancel out the laser phase noise, and we also find the same result for the symmetric Sagnac variable. The loss of the latter variable would be particularly unfortunate since this variable also cancels out gravitational wave signal, allowing instrument noise in the detector to be isolated and measured. Fortunately, we have found a set of more complicated TDI variables, which we call Delta-Sagnac variables, one of which accomplishes the same goal as the symmetric Sagnac variable to good accuracy. Finally, however, as we investigate the effects of the flexing of the detector arms due to non-circular orbital motion, we show that all variables, including the interferometer variables, which survive the rotation-induced loss of direction symmetry, will not completely cancel laser phase noise when the armlengths are changing with time. This unavoidable problem will place a stringent requirement on laser stability of 5 Hz per root Hz.Comment: 12 pages, 2 figure

PERFORMANCE ANALYSIS OF WELCH PRODUCTS RECYCLED RUBBER SPACER BLOCK

The Midwest Roadside Safety Facility was contracted by Will Stein of the Iowa Department of Transportation to conduct dynamic bogie testing of a recyclable rubber guardrail spacer block manufactured by Welch Products, Inc. The scope of the work included the setup of both a standard, wood guardrail post blockout and the Welch Products recycled rubber blockout on a standard W150x13.5 steel post, as well as two component tests using a bogie vehicle. The bogie tests were conducted in accordance with previously accepted procedures to evaluate the performance of guardrail post blockouts made of non-standard materials

The iron cage of the profession: a critique on closure in the Australian accounting profession

This paper seeks to contribute to the literature on the process of closure that occurs within the constructs of professions. The discussion in this paper focuses on the professional accounting bodies in Australia and how they have devolved a form of bureaucratic control over the education process through the credentialing of membership and accreditation of accounting degrees. Weber\u27s theory of bureaucracy in conjunction with Closure theory provide the framework upon which this critique is drawn. Implicit in the regulatory role of the accounting bodies is the justification of the practice of accounting and the status of the members of the professional bodies. Once those within the professional associations accept the right of the professional bodies to determine the educational requirements for membership along with the practice of accreditation of curriculum forms the iron cage. The practice of accreditation and credentialing exists in other disciplines such as medicine, engineering and law so that there exists parallels for claiming a legitimate basis for the intervention of the professional accounting bodies

PERFORMANCE ANALYSIS OF WELCH PRODUCTS RECYCLED RUBBER SPACER BLOCK

The Midwest Roadside Safety Facility was contracted by Will Stein of the Iowa Department of Transportation to conduct dynamic bogie testing of a recyclable rubber guardrail spacer block manufactured by Welch Products, Inc. The scope of the work included the setup of both a standard, wood guardrail post blockout and the Welch Products recycled rubber blockout on a standard W150x13.5 steel post, as well as two component tests using a bogie vehicle. The bogie tests were conducted in accordance with previously accepted procedures to evaluate the performance of guardrail post blockouts made of non-standard materials

Bering Sea deep circulation: Water properties and geopotential

Deep temperature and silicate data from the Bering Sea demonstrate patterns that are consistent and allow inference of near-bottom circulation. The cold source water enters Kamchatka Strait and mainly moves toward the southeast through a narrow topographic gap and into Bowers Basin. There is also a narrow, coherent flow eastward, and eventually southeastward, near the steep flank of Bowers Ridge. At levels ~100–300 m above the bottom, there is a suggestion of upward motion near the margins of much of the deep Bering Sea. Near-bottom geopotential gradients, referred to 3000 db, are in agreement with flow inferred from water properties