Kinetics of the radiation-induced exchange reactions of H/sub 2/, D/sub 2/, and T/sub 2/: a review (open access)

Kinetics of the radiation-induced exchange reactions of H/sub 2/, D/sub 2/, and T/sub 2/: a review

Mixtures of H/sub 2/--T/sub 2/ or D/sub 2/--T/sub 2/ will exchange to produce HT or DT due to catalysis by the tritium ..beta.. particle. The kinetics of the reaction D/sub 2/ + T/sub 2/ = 2DT may play an important role in designing liquid or solid targets of D/sub 2/--DT--T/sub 2/ for implosion fusion, and distillation schemes for tritium cleanup systems in fusion reactors. Accordingly, we have critically reviewed the literature for information on the kinetics and mechanism of radiation-induced self-exchange reactions among the hydrogens. We found data for the reaction H/sub 2/ + T/sub 2/ = 2HT in the gas phase and developed a scheme based on these data to predict the halftime to equilibrium for any gaseous H/sub 2/ + T/sub 2/ mixture at ambient temperature with an accuracy of +-10 percent. The overall order of the H/sub 2/ + T/sub 2/ = 2HT reaction is 1.6 based on an initial rate treatment of the data. The most probable mechanism for radiation-induced self-exchange reaction is an ion-molecule chain mechanism.
Date: January 6, 1978
Creator: Pyper, J.W. & Briggs, C.K.
Object Type: Report
System: The UNT Digital Library
Heat exchanger method: ingot casting; fixed abrasive method: multi-wire slicing (Phase II). Silicon sheet growth development for the Large Area Silicon Sheet Task of the Low Cost Silicon Solar Array Project. Quarterly progress report No. 1, November 21, 1977--December 31, 1977 (open access)

Heat exchanger method: ingot casting; fixed abrasive method: multi-wire slicing (Phase II). Silicon sheet growth development for the Large Area Silicon Sheet Task of the Low Cost Silicon Solar Array Project. Quarterly progress report No. 1, November 21, 1977--December 31, 1977

A high degree of crystallinity has been achieved in ingots cast. Since most of the growth took place near the solidification temperature, the top portion of the ingot was solidified by freezing from the surface. The thickness of this layer was reduced with the control of thermal flow characteristics in the furnace. The crucibles used in this study have a nonuniform bottom which is not conducive to proper heat transfer during solidification. In an effort to achieve high packing density of solar cells in the module with maximum material utilization, an attempt was made to cast a square cross-section ingot. Even though some minor cracking occurred in the first ingot, it appears feasible to cast square cross-section ingots by the Heat Exchanger Method. Higher feed forces results in higher cutting rates. However, this is accompanied by wire wander and increased surface damage depth. It has been established that the life of an impregnated blade can be prolonged by plating it after impregnation.
Date: January 6, 1978
Creator: Schmid, F. & Khattak, C.P.
Object Type: Report
System: The UNT Digital Library
Determination of trace impurities in uranium hexafluoride by an inductively coupled argon plasma spectrometer (open access)

Determination of trace impurities in uranium hexafluoride by an inductively coupled argon plasma spectrometer

A procedure has been developed to determine 21 trace impurity elements in uranium hexafluoride, using inductively coupled argon plasma emission spectrometry (ICAP). The method consists of a liquid-liquid extraction to separate uranium from the trace impurities with a mixture of tri-(2-ethyl-hexyl)-phosphate (TEHP) and heptane. The raffinate containing the elements is subsequently analyzed by ICAP. The impurity elements which can be analyzed by this method are: Al, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sb, Sn, Ti, V and Zn.
Date: January 6, 1983
Creator: Short, B. W.; Spring, H. S. & Grant, R. L.
Object Type: Report
System: The UNT Digital Library
Design note of an air-cooled 2 ft x 2 ft x 10. 5 ft long muon spoiler (open access)

Design note of an air-cooled 2 ft x 2 ft x 10. 5 ft long muon spoiler

This note describes the construction of a muon spoiler (magnetized steel assembly) with a cross section of 2 ft by 2 ft and a length of 10.5 ft. Two such spoilers are operated in series at an average field of about 15 kGauss, from one 100 ADC, 40 V power supply. The purpose of the spoilers is to prevent muons from easily escaping beyond the muon laboratory experimental area by bending them down so that they have to pass through more earth. The spoilers reduce the muon dose rate beyond the experimental area by about a factor of 15 to 20. These types of spoilers are not precision devices. They were inexpensive to build from scrap materials using rough flame cutting methods. It took about 14 days to fabricate them.
Date: January 6, 1988
Creator: Visser, A. & Pathiyil, J.
Object Type: Report
System: The UNT Digital Library
CHANGING THE SAFETY CULTURE IN HANFORD TANK FARMS (open access)

CHANGING THE SAFETY CULTURE IN HANFORD TANK FARMS

In 2000 the Hanford Tank Farms had one of the worst safety records in the Department of Energy Complex. By the end of FY08 the safety performance of the workforce had turned completely around, resulting in one of the best safety records in the DOE complex for operations of its kind. This paper describes the variety of programs and changes that were put in place to accomplish such a dramatic turn-around. The U.S. Department of Energy's 586-square-mile Hanford Site in Washington State was established during World War II as part of the Manhattan Project to develop nuclear materials to end the war. For the next several decades it continued to produce plutonium for the nation's defense, leaving behind vast quantities of radioactive and chemical waste. Much of this waste, 53,000,000 gallons, remains stored in 149 aging single-shell tanks and 28 newer double-shell tanks. One of the primary objectives at Hanford is to safely manage this waste until it can be prepared for disposal, but this has not always been easy. These giant underground tanks, many of which date back to the beginning of the Manhattan Project, range in size from 55,000 gallons up to 1.1 million gallons, and are buried …
Date: January 6, 2009
Creator: MV, BERRIOCHOA & LJ, ALCALA
Object Type: Article
System: The UNT Digital Library
Dose dependent effects of exercise training and detraining ontotal and regional adiposity in 4,663 men and 1,743 (open access)

Dose dependent effects of exercise training and detraining ontotal and regional adiposity in 4,663 men and 1,743

Objective: To determine if exercise reduces body weight andto examine the dose-response relationships between changes in exerciseand changes in total and regional adiposity. Methods and Results:Questionnaires on weekly running distance and adiposity from a largeprospective study of 3,973 men and 1,444 women who quit running(detraining), 270 men and 146 women who started running (training) and420 men and 153 women who remained sedentary during 7.4 years offollow-up. There were significant inverse relationships between change inthe amount of vigorous exercise (km/wk run) and changes in weight and BMIin men (slope+-SE:-0.039+-0.005 kg and -0.012+-0.002 kg/m2 per km/wk,respectively) and older women (-0.060+-0.018 kg and -0.022+-0.007 kg/m2per km/wk) who quit running, and in initially sedentary men(-0.098+-0.017 kg and -0.032+-0.005 kg/m2 per km/wk) and women(-0.062+-0.023 kg and -0.021+-0.008 kg/m2 per km/wk) who started running.Changes in waist circumference were also inversely related to changes inrunning distance in men who quit (-0.026+-0.005 cm per km/wk) or startedrunning (-0.078+-0.017 cm per km/wk). Conclusions. The initiation andcessation of vigorous exercise decrease and increase body weight andintra-abdominal fat, respectively, and these changes are proportional tothe change in exercise dose.
Date: January 6, 2006
Creator: Williams, Paul T. & Thompson, Paul D.
Object Type: Article
System: The UNT Digital Library
Fundamental Mechanisms of Interface Roughness (open access)

Fundamental Mechanisms of Interface Roughness

Publication quality results were obtained for several experiments and materials systems including: (i) Patterning and smoothening of sapphire surfaces by energetic Ar+ ions. Grazing Incidence Small Angle X-ray Scattering (GISAXS) experiments were performed in the system at the National Synchrotron Light Source (NSLS) X21 beamline. Ar+ ions in the energy range from 300 eV to 1000 eV were used to produce ripples on the surfaces of single-crystal sapphire. It was found that the ripple wavelength varies strongly with the angle of incidence of the ions, which increase significantly as the angle from normal is varied from 55° to 35°. A smooth region was found for ion incidence less than 35° away from normal incidence. In this region a strong smoothening mechanism with strength proportional to the second derivative of the height of the surface was found to be responsible for the effect. The discovery of this phase transition between stable and unstable regimes as the angle of incidence is varied has also stimulated new work by other groups in the field. (ii) Growth of Ge quantum dots on Si(100) and (111). We discovered the formation of quantum wires on 4° misoriented Si(111) using real-time GISAXS during the deposition of Ge. …
Date: January 6, 2009
Creator: Headrick, Randall L.
Object Type: Report
System: The UNT Digital Library
Resonance--Continuum Interference in Light Higgs Boson Production at a Photon Collider (open access)

Resonance--Continuum Interference in Light Higgs Boson Production at a Photon Collider

We study the effect of interference between the Standard Model Higgs boson resonance and the continuum background in the process {gamma}{gamma} {yields} H {yields} b{bar b} at a photon collider. Taking into account virtual gluon exchange between the final-state quarks, we calculate the leading corrections to the height of the resonance for the case of a light (m{sub H} < 160 GeV) Higgs boson. We find that the interference is destructive and around 0.1-0.2% of the peak height, depending on the mass of the Higgs and the scattering angle. This suppression is smaller by an order of magnitude than the anticipated experimental accuracy at a photon collider. However, the fractional suppression can be significantly larger if the Higgs coupling to b quarks is increased by physics beyond the Standard Model.
Date: January 6, 2009
Creator: Dixon, Lance J.; Sofianatos, Yorgos & /SLAC /Stanford U., Phys. Dept.
Object Type: Article
System: The UNT Digital Library
STATUS OF MECHANICAL SLUDGE REMOVAL AND COOLING COILS CLOSURE AT THE SAVANNAH RIVER SITE - F TANK FARM CLOSURE PROJECT - 9225 (open access)

STATUS OF MECHANICAL SLUDGE REMOVAL AND COOLING COILS CLOSURE AT THE SAVANNAH RIVER SITE - F TANK FARM CLOSURE PROJECT - 9225

The Savannah River Site F-Tank Farm Closure project has successfully performed Mechanical Sludge Removal using the Waste on Wheels (WOW) system within two of its storage tanks. The Waste on Wheels (WOW) system is designed to be relatively mobile with the ability for many components to be redeployed to multiple tanks. It is primarily comprised of Submersible Mixer Pumps (SMPs), Submersible Transfer Pumps (STPs), and a mobile control room with a control panel and variable speed drives. These tanks, designated as Tank 6 and Tank 5 respectively, are Type I waste tanks located in F-Tank Farm (FTF) with a capacity of 2839 cubic meters (750,000 gallons) each. In addition, Type I tanks have 34 vertically oriented cooling coils and two horizontal cooling coil circuits along the tank floor. DOE intends to remove from service and operationally close Tank 5 and Tank 6 and other HLW tanks that do not meet current containment standards. After obtaining regulatory approval, the tanks and cooling coils will be isolated and filled with grout for long term stabilization. Mechanical Sludge Removal of the remaining sludge waste within Tank 6 removed {approx} 75% of the original 25,000 gallons in August 2007. Utilizing lessons learned from Tank …
Date: January 6, 2009
Creator: Jolly, R
Object Type: Article
System: The UNT Digital Library
Outrunning major weight gain: a prospective study of 8,340consistent runners during 7 years of follow-up (open access)

Outrunning major weight gain: a prospective study of 8,340consistent runners during 7 years of follow-up

Background: Body weight increases with aging. Short-term,longitudinal exercise training studies suggest that increasing exerciseproduces acute weight loss, but it is not clear if the maintenance oflong-term, vigorous exercise attenuates age-related weight gain inproportion to the exercise dose. Methods: Prospective study of 6,119 maleand 2,221 female runners whose running distance changed less than 5 km/wkbetween their baseline and follow-up survey 7 years later. Results: Onaverage, men who ran modest (0-24 km/wk), intermediate (24-48 km/wk) orprolonged distances (>_48 km/wk) all gained weight throughage 64,however, those who ran ?48 km/wk had one-half the average annual weightgain of those who ran<24 km/wk. Age-related weight gain, and itsreduction by running, were both greater in younger than older men. Incontrast, men s gain in waist circumference with age, and its reductionby running, were the same in older and younger men. Women increased theirbody weight and waist and hip circumferences over time, regardless ofage, which was also reduced in proportion to running distance. In bothsexes, running did not attenuate weight gain uniformly, but ratherdisproportionately prevented more extreme increases. Conclusion: Men andwomen who remain vigorously active gain less weight as they age and thereduction is in proportion to the exercise dose.
Date: January 6, 2006
Creator: Williams, Paul T.
Object Type: Article
System: The UNT Digital Library
What's Inside the Black Box - Explaining Performance Assessment to Stakeholders (open access)

What's Inside the Black Box - Explaining Performance Assessment to Stakeholders

The performance assessment (PA) process is being applied to support an increasing variety of waste management decisions that involve the whole spectrum of stakeholders. As with many technical tools, the PA process can be seen as a black box, which can be difficult to understand when implemented. Recognizing the increasing use of PA and the concerns about difficulties with understanding, the Savannah River Site Citizens Advisory Board (CAB) made a recommendation that the U.S. Department of Energy (DOE) provide a Public Educational Forum on PAs. The DOE-Headquarters Environmental Management (DOE-EM) Office of Compliance and the DOE-Savannah River (DOE-SR) responded to this recommendation by supporting the Savannah River National Laboratory (SRNL) in developing several presentation modules that can be used to describe different aspects of the PA process. For the Public Educational Forum, the PA modules were combined with presentations on DOE perspectives, historical modeling efforts at the Savannah River Site, and review perspectives from the U.S. Nuclear Regulatory Commission (NRC). The overall goals are to help the public understand how PAs are implemented and the rigor that is applied, and to provide insight into the use of PAs for waste management decision-making.
Date: January 6, 2009
Creator: Seitz, R. & Elmer Wilhite, E.
Object Type: Article
System: The UNT Digital Library
Self-selection contributes significantly to the lower adiposity offaster, longer-distanced, male and female walkers (open access)

Self-selection contributes significantly to the lower adiposity offaster, longer-distanced, male and female walkers

Although cross-sectional studies show active individuals areleaner than their sedentary counterparts, it remains to be determined towhat extent this is due to initially leaner men and women choosing toexercise longer and more intensely (self-selection bias). In this reportwalking volume (weekly distance) and intensity (speed) were compared tocurrent BMI (BMIcurrent) and BMI at the start of walking (BMIstarting) in20,353 women and 5,174 men who had walked regularly for exercise for 7.2and 10.6 years,respectively. The relationships of BMIcurrent andBMIstarting with distance and intensity were nonlinear (convex). Onaverage, BMIstarting explained>70 percent of the association betweenBMIcurrent and intensity, and 40 percent and 17 percent of theassociation between BMIcurrent and distance in women and men,respectively. Although the declines in BMIcurrent with distance andintensity were greater among fatter than leaner individuals, the portionsattributable to BMIstarting remained relatively constant regardless offatness. Thus self-selection bias accounts for most of the decline in BMIwith walking intensity and smaller albeit significant proportions of thedecline with distance. This demonstration of self-selection is germane toother cross-sectional comparisons in epidemiological research, givenself-selection is unlikely to be limited to weight or peculiar tophysical activity.
Date: January 6, 2006
Creator: Williams, Paul T.
Object Type: Article
System: The UNT Digital Library
Novel Intermetallic Catalysts to Enhance PEM Membrane Durability (open access)

Novel Intermetallic Catalysts to Enhance PEM Membrane Durability

The research examined possible sources of degradation of platinum based anode catalysts under long term use. Scientists at the United Technologies Research Center had shown that the anode as well as the cathode catalysts degrade in hydrogen fuel cells. This goal of this research was to see if mechanisms of anode degradation could be understood using forefront electrochemical techniques in an aqueous system. We found that this method is limited by the very low levels of impurities (perhaps less than a part per trillion) in the electrolyte. This limitation comes from the relatively small catalyst surface area (a few sq cm or less) compared to the electrolyte volume of 10 to 25 ml. In real fuel cells this ratio is completelyreversed: high catalyst surface area and low electrolyte violume, making the system much less sensitive to impurities in the electrolyte. We conclude that degradation mechanisms should be studied in real fuel cell systems, rather than in ex-situ, large electrolyte volume experiments.
Date: January 6, 2009
Creator: DiSalvo, Francis J.
Object Type: Report
System: The UNT Digital Library
Why even active people get fatter--the asymmetric effects ofincreasing and decreasing exercise (open access)

Why even active people get fatter--the asymmetric effects ofincreasing and decreasing exercise

Background: Public health policies for preventing obesityneed guidelines for active individuals who are at risk due to exerciserecidivism. Methods: Changes in adiposity were compared to the runningdistances at baseline and follow-up in men and women whose reportedexercise increased (N=4,632 and 1,953, respectively) or decreased (17,280and 5,970, respectively) during 7.7 years of follow-up. Results: PerDelta km/wk, decreases in running distance caused over four-fold greaterweight gain between 0-8 km/wk (slope+-SE, males: -0.068+ -0.005 kg/m2,females: -0.080+-0.01 kg/m2) than between 32-48 km/wk (-0.017+-0.002 and-0.010+-0.005 kg/m2, respectively). In contrast, increases in runningdistance produced the smallest weight losses between 0-8 km/wk andstatistically significant weight loss only above 16 km/wk in males and 32km/wk in females. Above 32 km/wk (30 kcal/kg) in men and 16 km/wk (15kcal/kg) in women, weight loss from increasing exercise was equal to orgreater than weight gained with decreasing exercise, otherwise weightgain exceeded weight loss. Substantial weight gain occurred in runnerswho quit running, which would be mostly retained with resumed activity.Conclusion: Public health recommendations should warn against the risksof irreversible weight gain with exercise cessation. Weight gained due toreductions in exercise below 30 kcal/kg in men and 15 kcal/kg in womenmay not be reversed by resuming prior activity. Current IOM guidelines(i.e., maintain total …
Date: January 6, 2006
Creator: Williams, Paul T.
Object Type: Article
System: The UNT Digital Library
Advanced Thermoelectric Materials for Efficient Waste Heat Recovery in Process Industries (open access)

Advanced Thermoelectric Materials for Efficient Waste Heat Recovery in Process Industries

The overall objective of the project was to integrate advanced thermoelectric materials into a power generation device that could convert waste heat from an industrial process to electricity with an efficiency approaching 20%. Advanced thermoelectric materials were developed with figure-of-merit ZT of 1.5 at 275 degrees C. These materials were not successfully integrated into a power generation device. However, waste heat recovery was demonstrated from an industrial process (the combustion exhaust gas stream of an oxyfuel-fired flat glass melting furnace) using a commercially available (5% efficiency) thermoelectric generator coupled to a heat pipe. It was concluded that significant improvements both in thermoelectric material figure-of-merit and in cost-effective methods for capturing heat would be required to make thermoelectric waste heat recovery viable for widespread industrial application.
Date: January 6, 2009
Creator: Polcyn, Adam & Khaleel, Moe
Object Type: Report
System: The UNT Digital Library
Review of Systematic Investigations of the Rout/Rside ratio in HBT at RHIC (open access)

Review of Systematic Investigations of the Rout/Rside ratio in HBT at RHIC

We review the significant difference in the ratio R{sub out}/R{sub side} between experiment and theory in heavy-ion collisions at RHIC. This ratio is expected to be strongly correlated with the pion emission duration. Hydrodynamic models typically calculate a value that approximately equal to 1.5 and moderately dependent on k{sub T} whereas the experiments report a value close to unity and independent of k{sub T}. We review those calculations in which systematic variations in the theoretical assumptions were reported. We find that the scenario of second order phase transition or cross-over has been given insufficient attention, and may play an important role in resolving this discrepancy.
Date: January 6, 2005
Creator: Soltz, R. A.
Object Type: Article
System: The UNT Digital Library
Mass, quark-number, and sqrt sNN dependence of the second andfourth flow harmonics in ultra-relativistic nucleus-nucleuscollisions (open access)

Mass, quark-number, and sqrt sNN dependence of the second andfourth flow harmonics in ultra-relativistic nucleus-nucleuscollisions

We present STAR measurements of the azimuthal anisotropyparameter v_2 for pions, kaons, protons, Lambda, bar Lambda, Xi+bar Xi,and \Omega + bar Omega, along with v_4 for pions, kaons, protons, andLambda + bar Lambda at mid-rapidity for Au+Au collisions at sqrt sNN=62.4and 200 GeV. The v_2(p_T) values for all hadron species at 62.4 GeV aresimilar to those observed in 130 and 200 GeV collisions. For observedkinematic ranges, v_2 values at 62.4, 130, and 200 GeV are as little as10 percent-15 percent larger than those in Pb+Pb collisions at sqrt s NN=17.3 GeV. At intermediate transverse momentum (p_T from 1.5-5 GeV/c),the 62.4 GeV v_2(p_T) and v_4(p_T) values are consistent with thequark-number scaling first observed at 200 GeV. A four-particle cumulantanalysis is used to assess the non-flow contributions to pions andprotons and some indications are found for a smaller non-flowcontribution to protons than pions. Baryon v_2 is larger than anti-baryonv_2 at 62.4 and 200 GeV perhaps indicating either that the initialspatial net-baryon distribution is anisotropic, that the mechanismleading to transport of baryon number from beam- to mid-rapidity enhancesv_2, or that anti-baryon and baryon annihilation is larger in thein-plane direction.
Date: January 6, 2007
Creator: Abelev, B. I.; Adams, J.; Aggarwal, M. M.; Ahammed, Z.; Amonett,J.; Anderson, B. D. et al.
Object Type: Article
System: The UNT Digital Library
Identification and Protection of a Bat Colony in the 183-F Clearwell: Mitigation of Bat Habitat on the Hanford Site (open access)

Identification and Protection of a Bat Colony in the 183-F Clearwell: Mitigation of Bat Habitat on the Hanford Site

An ecological investigation was conducted to evaluate mitigation options for demolition of a retired facility that contained a maternity roost of approximately 2,000 Myotis yumanensis bats. The recommendation from the study was to leave the non-contaminated structure intact and fence the area.
Date: January 6, 2009
Creator: K. A. Gano, J. G. Lucas, C. T. Lindsey
Object Type: Report
System: The UNT Digital Library
REFERENCE CASES FOR USE IN THE CEMENTITIOUS BARRIERS PARTNERSHIP (open access)

REFERENCE CASES FOR USE IN THE CEMENTITIOUS BARRIERS PARTNERSHIP

The Cementitious Barriers Project (CBP) is a multidisciplinary cross cutting project initiated by the US Department of Energy (DOE) to develop a reasonable and credible set of tools to improve understanding and prediction of the structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. The period of performance is &gt;100 years for operating facilities and &gt; 1000 years for waste management. The CBP has defined a set of reference cases to provide the following functions: (1) a common set of system configurations to illustrate the methods and tools developed by the CBP, (2) a common basis for evaluating methodology for uncertainty characterization, (3) a common set of cases to develop a complete set of parameter and changes in parameters as a function of time and changing conditions, and (4) a basis for experiments and model validation, and (5) a basis for improving conceptual models and reducing model uncertainties. These reference cases include the following two reference disposal units and a reference storage unit: (1) a cementitious low activity waste form in a reinforced concrete disposal vault, (2) a concrete vault containing a steel high-level waste tank filled with grout (closed high-level waste tank), and (3) a spent …
Date: January 6, 2009
Creator: Langton, C
Object Type: Article
System: The UNT Digital Library
Search for Lepton Flavour Violating Decays tau- to l- Ks with the BaBar experiment (open access)

Search for Lepton Flavour Violating Decays tau- to l- Ks with the BaBar experiment

A search for the lepton flavor violating decays {tau}{sup -} {yields} l{sup -} K{sub S}{sup 0} (l = e or {mu}) has been performed using a data sample corresponding to an integrated luminosity of 469 fb{sup -1}, collected with the BABAR detector at the SLAC PEP-II e{sup +}e{sup -} asymmetric energy collider. No statistically significant signal has been observed in either channel and the estimated upper limits on branching fractions are {Beta}({tau}{sup -} {yields} e{sup -} K{sub S}{sup 0}) &lt; 3.3 x 10{sup -8} and {Beta}({tau}{sup -} {yields} {mu}{sup -}K{sub S}{sup 0}) &lt; 4.0 x 10{sup -8} at 90% confidence level.
Date: January 6, 2009
Creator: Aubert, B.; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E. et al.
Object Type: Article
System: The UNT Digital Library
Erythroblastic Islands: Specialized Mircoenvironmental Niches forErythropoiesis (open access)

Erythroblastic Islands: Specialized Mircoenvironmental Niches forErythropoiesis

This review focuses on current understanding of molecular mechanisms operating within erythroblastic islands including cell-cell adhesion, regulatory feedback, and central macrophage function. RECENT FINDINGS: Erythroblasts express a variety of adhesion molecules and recently two interactions have been identified that appear to be critical for island integrity. Erythroblast macrophage protein, expressed on erythroblasts and macrophages, mediates cell-cell attachments via homophilic binding. Erythroblast intercellular adhesion molecule-4 links erythroblasts to macrophages through interaction with macrophage alphav integrin. In intercellular adhesion molecule-4 knockout mice, erythroblastic islands are markedly reduced, whereas the erythroblast macrophage protein null phenotype is severely anemic and embryonic lethal. Retinoblastoma tumor suppressor (Rb) protein stimulates macrophage differentiation by counteracting inhibition of Id2 on PU.1, a transcription factor that is a crucial regulator of macrophage differentiation. Rb-deficient macrophages do not bind Rb null erythroblasts and the Rb null phenotype is anemic and embryonic lethal. Lastly, extruded nuclei rapidly expose phosphatidylserine on their surface, providing a recognition signal similar to apoptotic cells. SUMMARY: Although understanding of molecular mechanisms operating within islands is at an early stage, tantalizing evidence suggests that erythroblastic islands are specialized niches where intercellular interactions in concert with cytokines play critical roles in regulating erythropoiesis.
Date: January 6, 2006
Creator: Chasis, Joel Anne
Object Type: Article
System: The UNT Digital Library
Possible benefits from shuffling dipoles in the RHIC (open access)

Possible benefits from shuffling dipoles in the RHIC

An example is given which demonstrates how dipole shuffling can be done to minimize various effects of magnetic errors. The concepts of ''global'' and ''local'' compensation are explained. With a Gaussian distribution, it is found to be possible to achieve an improvement of factor four or five over the statistically expected values without too much sacrifice in nonlinear distortion. There was no difference found in the performance between shuffling eight dipoles and shuffling twelve, and the tune dependence of the performance is found to be acceptable when the change in tune is less than about 0.5. (LEW)
Date: January 6, 1986
Creator: Ohnuma, S.
Object Type: Report
System: The UNT Digital Library
Field shape measurements of prototype Main Injector dipole endpacks (open access)

Field shape measurements of prototype Main Injector dipole endpacks

Measurements of the transverse dependence of the flux on the symmetry plane were obtained on a series of endpacks mounted on a Main Injector prototype dipole. From these flux measurements, we determined the endfield shape, expressed in terms of normal harmonics, up to 14-pole. We describe the measurement and analysis procedure, and present the results for all endpacks that were tested. The final endpack (number 10) has a sextupole, normalized to the body, of +0.167 [plus minus] .072 units, and the relative field shape deviates by [lt] 1.2 units relative to the on-axis field strength over the range [vert bar]x[vert bar] [lt] 2.0[double prime]. These measurements indicate that Endpack 10 meets the requirements for the Main Injector dipole.
Date: January 6, 1993
Creator: Glass, H. D.; Brown, B. C. & Harding, D. J.
Object Type: Report
System: The UNT Digital Library
Particle characterization for geothermal operations (open access)

Particle characterization for geothermal operations

A detailed summary of an ongoing evaluation of existing particle measuring methodology with emphasis on (a) adapting of existing methods in geothermal operations and (b) further development of existing instrumentation for field use is presented. The various instruments and methods used and/or suggested for particle characterization are described in detail. Theoretical and practical aspects of particle characterizations are outlined. A plan for further laboratory and field experiments is outlined. The instrumentations to be selected after some additional lab and field tests will be used in the studies on (a) formation damage through particle invasion and (b) characterizing and monitoring of particle suspensions in geothermal operations.
Date: January 6, 1981
Creator: Vetter, O.J. & Kandarpa, V.
Object Type: Report
System: The UNT Digital Library