Low cycle fatigue behavior of conventionally cast MAR-M 200 AT 1000 deg C

The low cycle fatigue behavior of the nickel-based superalloy MAR-M 200 in conventionally cast form was studied at 1000 C. Continuous cycling tests, without hold times, were conducted with inelastic strain ranges of from 0.04 to 0.33 percent. Tests were also conducted which included a hold time at peak strain in either tension or compression. For the conditions studied, it was determined that imposition of hold times did not significantly affect the fatigue life. Also, for continuous cycling tests, increasing or decreasing the cycle frequency did not affect life. Metallographic analysis revealed that the most significant damage mechanism involved environmentally assisted intergranular crack initiation and propagation, regardless of the cycle type. Changes in the gamma morphology (rafting and rod formation) were observed, but did not significantly affect the failure

Low cycle fatigue of MAR-M 200 single crystals at 760 and 870 deg C

Fully reversed low cycle fatigue tests were conducted on single crystals of the nickel-base superalloys Mar-M 200 at 760 C and 870 C. At 760 C, planar slip (octahedral) lead to orientation-dependent strain hardening and cyclic lives. Multiple slip crystals strain hardened the most, resulting in relatively high stress ranges and low lives. Single slip crystals strain hardened the least, resulting in relatively low stress ranges and higher lives. A preferential crack initiation site which was related to slip plane geometry was observed in single slip orientated crystals. At 870 C, the trends were quite different, and the slip character was much more homogeneous. As the tensile axis orientation deviated from 001 , the stress ranges increased and the cyclic lives decreased. Two possible mechanisms were proposed to explain the behavior: one is based on Takeuchi and Kuramoto's cube cross-slip model, and the other is based on orientation-dependent creep rates

Techniques for improving reliability of computers

Modular design techniques improve methods of error detection, diagnosis, and recovery. Theoretical computer (MARCS (Modular Architecture for Reliable Computer Systems)) study deals with postulated and modeled technology indigenous to 1975-1980. Study developments are discussed

Town of Colonial Beach Survey of Central and Castlewood Beaches

The Town of Colonial Beach occupies a peninsula between the Potomac River and Monroe Bay. Approximately 2.5 miles of the shoreline is publicly-owned. Two areas on the Potomac River have been enhanced as recreational beaches for swimming and sunbathing. Central Beach is located just south of the Town Pier and is the main recreational beach. Castlewood Beach is south of Central Beach near the entrance to Monroe Bay

Parrotts Creek Dredge Channel Data Report

Parrotts Creek is located along the Rappahannock River in Middlesex County, VA. The mouth of the creek is about 850 ft wide, but just inside the mouth of the creek, a spit extends from the upland narrowing the creek to about 300 ft before it widens again. Overall, this is a relatively short, undeveloped creek. Most of the development (wharfs, ramps, piers) occur near the mouth. Most of the more inland areas of the creek are surrounded by woodland. The federally-authorized channel was established in 1955 due to the presence of a public ramp and landing area, as well as oyster and seafood packing houses located on the creek. It is a 4,800 ft long, 60 ft wide channel with a 120 ft by 120 ft turning basin, and a controlling depth of -6 ft MLLW. (...

Microcallus formation from maize protoplasts prepared from embryogenic callus

Conditions have been developed that induce maize ( Zea mays L.) protoplasts to re-synthesize cell walls and to initiate cell divisions. Two types of embryogenic maize callus were used as a source of protoplasts: a heterogeneous callus (Type I) derived from immature embryos after three weeks in culture, and a friable, rapidly growing callus (Type II) selected from portions of the Type I callus. Many variables in the growth conditions of the donor tissue (type of medium, transfer schedule, age of callus), protoplast isolation solutions (pH, osmolarity, type and concentration of cell wall hydrolyzing enzymes, addition of polyamines) and conditions (amount of time in enzyme, amount of tissue per volume of enzyme incubation medium, agitation, preplasmolysis of source tissue, type of callus), and purification procedures (filtration and-or flotation), were found to affect both yield and viability of protoplasts (based upon fluorescein-diacetate staining). Our isolation procedure yielded high numbers of viable, uninucleated maize callus protoplasts which were densely cytoplasmic and varied in size from 20 to 50 μm in diameter. Protoplasts plated in solid medium formed walls and divided several times. Of several gelling agents tested for protoplast propagation, only agarose resulted in protoplasts capable of sustained divisions leading to the formation of microcalli. Plating efficiency was established over a wide range of protoplast densities (10 3 –10 7 protoplasts/ml). Highest plating efficiency (25%) was obtained at 1·10 6 protoplasts/ml). The resulting microcalli grew to be dense clusters of about 0.1–0.5 mm in diameter and then stopped growing. Nurse cultures of maize and carrot ( Daucus carota L.), were used to establish that individual protoplasts (not contaminating cells or cell clusters) formed walls and divided. Nurse cultures also increased the efficiency of microcallus formation from protoplasts.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47471/1/425_2004_Article_BF00392367.pd

Solar Flare Impulsive Phase Observations from SDO and Other Observatories

With the start of normal operations of the Solar Dynamics Observatory in May 2010, the Extreme ultraviolet Variability Experiment (EVE) and the Atmospheric Imaging Assembly (AIA) have been returning the most accurate solar XUV and EUV measurements every 10 and 12 seconds, respectively, at almost 100% duty cycle. The focus of the presentation will be the solar flare impulsive phase observations provided by EVE and AIA and what these observations can tell us about the evolution of the initial phase of solar flares. Also emphasized throughout is how simultaneous observations with other instruments, such as RHESSI, SOHO-CDS, and HINODE-EIS, will help provide a more complete characterization of the solar flares and the evolution and energetics during the impulsive phase. These co-temporal observations from the other solar instruments can provide information such as extending the high temperature range spectra and images beyond that provided by the EUV and XUV wavelengths, provide electron density input into the lower atmosphere at the footpoints, and provide plasma flows of chromospheric evaporation, among other characteristics

Northern Neck Regional Shallow Draft Channel Dredging Plan: Initial Phase

The purpose of this project is to develop a regional dredging program for the localities of the Northern Neck. This report encompasses Phase 1 of the project, which included creating a database of waterbodies in Lancaster, Northumberland, Richmond, and Westmoreland Counties and the Town of Colonial Beach along the Potomac and Rappahannock Rivers and Chesapeake Bay. Generally, these waterbodies can be categorized into three basic types of shallow draft channels: federally-authorized to include aids to navigation (ATONS), non-federal with ATONS, and non-federal without ATONs. Along the Northern Neck, presently identified, are 13 federal channels, 37 non-federal channels in creeks with ATONs, and 92 in creeks without defined channels or ATONs, for a total of 142 waterbodies. Additional non-federal creeks, coves, branches, and ponds (all are interchangeably identified as waterbodies in this report) occur in these localities, but the analysis was limited to waterbodies that had some residential or economic usage. These waterbodies occur in Lancaster (35 waterbodies), Northumberland (67 waterbodies), Richmond (4 waterbodies), and Westmoreland (31 waterbodies) counties. To avoid double counting of waterbodies, 5 additional waterbodies that are located on the boundaries of these counties were attributed to just one county for this report. These waterbodies have been grouped within one of their boundary counties bringing the number of waterbodies in Lancaster to 38 and Westmoreland to 33. Physical parameter data was collected or created for each of these waterbodies. These data included creek mouth morphology, amount of shoaling in the waterbody mouth, waterbody type (primary, secondary, etc.), water surface area, combined shoreline length, historical (1971- 2020) and current (2016-2020) SAV presence, private and public oyster lease presence and the amount of area they cover, number of remotely-sensed coastal structures such as piers, marinas, boat ramps, and verified economic facilities such as marinas and other mooring places, resource, seafood related, and transportation facilities that impact the locality’s economics. Utilizing the collected data, the steps that localities need to take for additional data collection to develop a dredging project were outlined, and recommendations were made for additional regional management considerations for use in Phases 2 and 3. Finally, next steps were suggested. By creating a regional program for dredging of shallow water, localities can save time, effort, and money. Such a program also provides ways for localities to plan for the utilization of dredge material to combat repetitive flooding and improve coastal resiliency

Microcallus growth from maize protoplasts

Maize ( Zea mays L. ) protoplasts obtained from Type I and Type II calli from several genotypes were shown to be capable of synthesizing cell walls and forming small clusters of cells. The medium used also supported cluster formation from protoplasts obtained from root tips. The effects of various additions to the medium (such as casein hydrolysate, coconut water, amino acids, sugars, phytohormones, nitrate, calcium, and dimethylsulfoxide as well as pH variations on cellcluster formation were determined. The method of culture (protoplasts plated in agarose or supported in alginate beads in liquid medium) as well as several components of the medium were found to be critical for microcallus formation. Protoplasts obtained from embryogenic Type I callus and cultured in the medium of C. Nitsch and J.P. Nitsch (1967, Planta 72 , 355–370) modified by various additions (NN 67-mod medium) were affected most by various sugars, casein hydrolysate, coconut water, and a combination of the auxins napthalene-1-acetic acid (2 mg/l) and 2,4-dichlorophenoxyacetic acid (0.1 mg/l), and the cytokinin N 6 -benzylaminopurine (0.5 mg/l). Cluster size in the agarose culture system was from 0.1 to 0.5 mm diameter and in the alginate culture system, up to 2.0 mm diameter.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47472/1/425_2004_Article_BF00395067.pd