Transgenic expression of the Ly49A natural killer cell receptor confers class I major histocompatibility complex (MHC)-specific inhibition and prevents bone marrow allograft rejection.

Natural killer (NK) cells and some T cells are endowed with receptors specific for class I major histocompatibility complex (MHC) molecules that can inhibit cellular effector functions. The function of the Ly49 receptor family has been studied in vitro, but no gene transfer experiments have directly established the role of these receptors in NK cell functions. We show here that transgenic expression of the H-2Dd-specific Ly49A receptor in all NK cells and T cells conferred class I-specific inhibition of NK cell-mediated target cell lysis as well as of T cell proliferation. Furthermore, transgene expression prevented NK cell-mediated rejection of allogeneic H-2d bone marrow grafts by irradiated mice. These results demonstrate the function and specificity of Ly49 receptors in vivo, and establish that their subset-specific expression is necessary for the discrimination of MHC-different cells by NK cells in unmanipulated mice

The world crisis: global financial governance: principles of reform

It is now increasingly acknowledged that complex global processes, from the financial to the ecological, connect the fate of communities across the world. Yet the problem-solving capacity of the existing system of global institutions is in many areas not effective, accountable, or fast enough to resolve current global dilemmas. What has recently been called the paradox of our times refers to the fact that the collective issues we must grapple with are of growing extensity and intensity, and yet the means for addressing them are weak and incomplete.1 There are a variety of reasons for the persistence of these problems, but at the most basic level the persistence of this paradox remains an issue of governance. One significant problem in this regard is that a growing number of issues span both the domestic and the international domains. The institutional fragmentation and competition between states can lead to these global issues being addressed in an ad hoc and dissonant manner. A second problem is that even when the global dimension of a problem is acknowledged, there is no clear division of labour among the myriad of international institutions that seek to address them: their functions often overlap, their mandates conflict, and their objectives often become blurred. A third problem is that the existing system of global governance suffers from severe deficits of accountability and inclusion. This problem is especially relevant in regard to how less economically powerful states and, hence, their entire populations, are marginalised or excluded from decisionmaking. This paper describes the current global economic crisis as intimately related to a problem of governance, and articulates simple principles by which the reform of governance can be guided. Increased accountability through participatory reform, we argue, helps to underwrite effectiveness

Modeling and control of a silicon substrate heater for carbon nanotube growth experiments

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (leaf 26).The precision engineering research group at MIT is working on carbon nanotube growth experiments on silicon substrates and in microfabricated silicon devices, to try to produce improved bulk nanotube growth. For this thesis, a heating control system was designed and implemented for eventual use in CNT growth experiments. The computer program that controls the heater is user-adaptable, so that an experimenter can easily change the desired temperatures at various points of the process. Later, this heating system will become part of a much larger system that also incorporates a controlled flow rate. The goal of the system is to achieve high-bandwidth control of reaction conditions. In the heating control system designed, a computer controls a power supply attached to a wire-wrapped silicon chip, which is used to heat up the system, and the temperature is measured by a thermocouple. The control algorithm uses proportional gain, and the output is a PWM voltage. For accurate control of the system, a goal was set out to achieve an error of within 10%. For gains above 5, the computer can accurately control the temperature to less than 5.5% of the desired values in steady state, and an error of 0.75% was achieved with a gain of 50.(cont.) Thus the system meets the desired specification of error. Also, while the error drops dramatically with increasing gain, the overshoot increases much more slowly, making a higher gain desirable. Also, the system still has only reached temperatures of 650 degrees Celsius, although temperatures of 1000 degrees Celsius are required for nanotube growth. In order to achieve this, further tests will be performed with thicker wire and more voltage. Also, contact resistances within the chromel decrease with increasing temperatures, which reduce the percentage of power dissipated in the chromel compared to the lead wires. If the system is modified to eliminate this effect, by wrapping the wire differently or by using doped silicon, higher temperatures can be achieved. This will also make the system more predictable, leading to a better model and better control. Finally, to improve overall performance, one can experiment with changes to the switching time, using a PI or PID controller, and active cooling.by David Held.S.B

Coverage-dependent molecular tilt of carbon monoxide chemisorbed on Pt{110}: A combined LEED and DFT structural analysis

The adsorption of carbon monoxide on the Pt{110} surface at coverages of 0.5 ML and 1.0 ML was investigated using quantitative low-energy electron diffraction (LEED IV) and density-functional theory (DFT). At 0.5 ML CO lifts the reconstruction of the clean surface but does not form an ordered overlayer. At the saturation coverage, 1.0 ML, a well-ordered p(2×1) superstructure with glide line symmetry is formed. It was confirmed that the CO molecules adsorb on top of the Pt atoms in the top-most substrate layer with the molecular axes tilted by ±22° with respect to the surface normal in alternating directions away from the close packed rows of Pt atoms. This is accompanied by significant lateral shifts of 0.55 Å away from the atop sites in the same direction as the tilt. The top-most substrate layer relaxes inwards by −4% with respect to the bulk-terminated atom positions, while the consecutive layers only show minor relaxations. Despite the lack of long-range order in the 0.5 ML CO layer it was possible to determine key structural parameters by LEED IV using only the intensities of the integer-order spots. At this coverage CO also adsorbs on atop sites with the molecular axis closer to the surface normal (b10°). The average substrate relaxations in each layer are similar for both coverages and consistent with DFT calculations performed for a variety of ordered structures with coverages of 1.0 ML and 0.5 ML

TRAP CROP RADISH: A SUSTAINABLE ALTERNATIVE FOR NEMATICIDE IN SUGAR BEETS

Chemical treatment of nematodes in sugar beets can be very costly ($190 per acre), and hazardous, representing significant environmental risks to air, water and human health. Substituting trap crop radish for chemicals, represents a win-win case of sustainable pest control, yielding environmental benefits, higher profit and reduced risk.Crop Production/Industries,