Process comparison study. MSFC Center Director's Discretionary Fund (CDDF)

A process comparison study was conducted using four different advanced manufacturing techniques to fabricate a composite solid rocket booster systems tunnel cover. Costs and labor hours were tracked to provide the comparison between the processes. A relative structural comparison of the components is also included. The processes utilized included filament winding, pultrusion, automated tape laying, and thermoplastic thermoforming. The hand layup technique is also compared. Of the four advanced processes evaluated, the thermoformed thermoplastic component resulted in the least total cost. The automated tape laying and filament winding techniques closely followed the thermoplastic component in terms of total cost; and, these techniques show the most promise for high quality components and lower production costs. The pultruded component, with its expensive tooling and material requirements, was by far the most expensive process evaluated, although the results obtained would not be representative of large production runs

If We Pay Football Players, Why Not Kidney Donors

Ethicists who oppose compensating kidney donors claim they do so because kidney donation is risky for the donor’s health, donors may not appreciate the risks and may be cognitively biased in other ways, and donors may come from disadvantaged groups and thus could be exploited. However, few ethical qualms are raised about professional football players, who face much greater health risks than kidney donors, have much less counseling and screening concerning that risk, and who often come from racial and economic groups deemed disadvantaged. It thus seems that either ethicists—and the law—should ban both professional football and compensated organ donation, allow both, or allow compensated organ donation but prohibit professional football. The fact that we choose none of those options raises questions about the wisdom of the compensation ba

If We Allow Football Players and Boxers to be Paid for Entertaining the Public, Why Don’t We Allow Kidney Donors to be Paid for Saving Lives?

We contrast the compensation ban on organ donation with the legal treatment of football, boxing, and other violent sports where both acute and chronic injuries to participants are common. Our claim is that there is a stronger case for compensating kidney donors than for compensating participants in violent sports. If this proposition is accepted, one implication is that there are only three logically consistent positions: allow compensation for both kidney donation and for violent sports; allow compensation for kidney donation but not for violent sports; or allow compensation for neither. Our current law and practice is perverse in endorsing a fourth regime, allowing compensation for violent sports but not kidney donation. We base our argument chiefly on the medical risk to participants, the consent process, social justice concerns, and social welfare considerations. The medical risks to a professional career in football, boxing, and other violent sports are much greater both in the near and long term than the risks of donating a kidney. On the other hand, the consent and screening process in professional sports is not as developed as in kidney donation. The social justice concerns stem from the fact that most players are black and some come from impoverished backgrounds. Finally, the net social benefit from compensating kidney donors – namely, saving thousands of lives each year and reducing the suffering of 100,000 more receiving dialysis – far exceeds the net social benefit of entertaining the public through professional sports. In sum, the arguments against compensating kidney donors apply with equal or greater force to compensating athletes in these sport

A Primer on Kidney Transplantation: Anatomy of the Shortage

Kidneys are unique among the solid organs due to the combination of the low risk of living donation, the feasibility of sustaining life on dialysis for several years following kidney failure, and Medicare coverage of dialysis and transplantation for kidney patients. Despite these advantages, thousands of Americans die each year while waiting for a kidney transplant, and the waiting list grows each year. In this kidney transplantation primer, we provide a quantitative description of the kidney shortage and discuss future trends and possible solutions. We demonstrate that the current system provides only about half as many kidneys as are needed for transplantation and the gap cannot be eliminated through an increase in deceased donation alone, because most kidneys from suitable deceased donors are already procured. The prospects for increasing living donations under the current system are also dim. Donations from living kidney donors have declined from their 2003 peak and nearly all living kidney donations are directed by the donor, usually to family members, rendering the current account of living kidney donation as “altruistic” somewhat misleading. For all of these reasons, we believe the time is ripe to reconsider financial incentives for kidney donation. Needless to say, a system that provided financial rewards for living donors could produce unsavory consequences, and would have to be carefully designed and managed. But without such a system, the most likely version of the future is a continuation of unnecessarily high rates of death and disability from kidney failure

If We Pay Football Players, Why Not Kidney Donors

Ethicists who oppose compensating kidney donors claim they do so because kidney donation is risky for the donor’s health, donors may not appreciate the risks and may be cognitively biased in other ways, and donors may come from disadvantaged groups and thus could be exploited. However, few ethical qualms are raised about professional football players, who face much greater health risks than kidney donors, have much less counseling and screening concerning that risk, and who often come from racial and economic groups deemed disadvantaged. It thus seems that either ethicists—and the law—should ban both professional football and compensated organ donation, allow both, or allow compensated organ donation but prohibit professional football. The fact that we choose none of those options raises questions about the wisdom of the compensation ba

Spin Polarized Current in the Ground State of Superconductor - Ferromagnet - Insulator Trilayers

We study the ground state properties of a superconductor - ferromagnet - insulator trilayer on the basis of a Hubbard Model featuring exchange splitting in the ferromagnet and electron - electron attraction in the superconductor. We solve the spin - polarized Hartree - Fock - Gorkov equations together with the Maxwell's equation (Ampere's law) fully self-consistently. For certain values of the exchange splitting we find that a spontaneous spin polarized current is generated in the ground state and is intimately related to Andreev bound states at the Fermi level. Moreover, the polarization of the current strongly depends on the band filling.Comment: 13 pages, 14 figure

Fulde-Ferrell-Larkin-Ovchinnikov-like state in Ferromagnet-Superconductor Proximity System

We discuss some properties of the ferromagnet-superconductor proximity system. In particular, the emphasis is put on the physics of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) like state. In addition to Andreev reflections it features a number of unusual thermodynamic and transport properties, like: oscillatory behavior of the pairing amplitude, density of states and superconducting transition temperature as a function of the ferromagnet thickness. Surprisingly, under certain conditions spontaneous spin polarized current is generated in the ground state of such a system. We provide some informations regarding experimental observations of this exotic state.Comment: Talk given at Advanced Research Workshop on ''Physics of Spin in Solids: Materials, Methods & Applications'', Baku (October 2003

Spontaneous currents in a ferromagnet - normal metal - superconductor trilayer

We discuss the ground state properties of the system composed of a normal metal sandwiched between ferromagnet and superconductor within a tight binding Hubbard model. We have solved the spin-polarized Hartree-Fock-Gorkov equations together with the Maxwell's equation (Ampere's law) and found a proximity induced Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state in this system. Here we show that the inclusion of the normal metal layer in between those subsystems does not necessarily lead to the suppression of the FFLO phase. Moreover, we have found that depending on the thickness of the normal metal slab the system can be switched periodically between the state with the spontaneous current flowing to that one with no current. All these effects can be explained in terms of the Andreev bound states formed in such structures.Comment: 6 pages, 4 figure

Thermoelectric phenomena in a quantum dot asymmetrically coupled to external leads

We study thermoelectric phenomena in a system consisting of strongly correlated quantum dot coupled to external leads in the Kondo regime. We calculate linear and nonlinear electrical and thermal conductance and thermopower of the quantum dot and discuss the role of asymmetry in the couplings to external electrodes. In the linear regime electrical and thermal conductances are modified, while thermopower remains unchanged. In the nonlinear regime the Kondo resonance in differential conductance develops at non-zero source-drain voltage, which has important consequences on thermoelectric properties of the system and the thermopower starts to depend on the asymmetry. We also discuss Wiedemann-Franz relation, thermoelectric figure of merit and validity of the Mott formula for thermopower.Comment: 6 pages, 7 figure