Description of a magnetic bearing test fixture

A description of a microcomputer controlled magnetic bearing test fixture is presented. Parameters which are controlled are magnetic bearing current and gaps. Parameters which are measured are magnetic bearing gaps, magnetic flux in the bearing gaps, and bearing forces. The test fixture is configured for bearing elements similar to those used in a laboratory test model Annular Momentum Control Device (AMCD)

Weighing the costs and benefits of climate change to our children

Our efforts to put the brakes on climate change or adapt to a warming climate present a fundamental tradeoff between costs borne today and benefits that accrue to the children and grandchildren of the current generation. In making investments today that affect future generations’ prospects, we need to think carefully about how we value their welfare compared to our own. A common economic formula recommends giving up only 5 cents today for every dollar of benefits 100 years in the future; we call this discounting the future. Underlying this approach is the assumption that future generations will be much better off than our own, just as we are much wealthier than our ancestors were. Would our descendants’ agree with this approach? Are there reasons to put more value on future benefits? William Pizer, Ben Groom, and Simon Dietz discuss three possible reasons that we might put a higher value on future benefits. First, people disagree considerably about the correct discount rate. Other plausible interpretations of society’s preferences or observed data could increase the weight we place on future benefits by as much as a factor of five. Second, we may have failed to correctly value future climate change impacts, particularly those related to the loss of environmental amenities that have no close monetary substitutes. Third, we may not be properly valuing the risk that a warming climate could cause sudden and catastrophic changes that would drastically alter the size of the population. Ultimately, the authors write, many of the choices about how we value future generations’ welfare come down to ethical questions, and many of the decisions we must make come down to societal preferences—all of which will be difficult to extract from data or theory

Declining discount rates

We ask whether the US government should replace its current discounting practices with a declining discount rate schedule, as the United Kingdom and France have done, or continue to discount the future at a constant exponential rate. We present the theoretical basis for a declining discount rate (DDR) schedule, but focus on how, in practice, a DDR could be estimated for use by policy analysts. We discuss the empirical approaches in the literature and review how the United Kingdom and France estimated their DDR schedules. We conclude with advice on how the United States might proceed to consider modifying its current discounting practices

Palatini approach to Born-Infeld-Einstein theory and a geometric description of electrodynamics

The field equations associated with the Born-Infeld-Einstein action are derived using the Palatini variational technique. In this approach the metric and connection are varied independently and the Ricci tensor is generally not symmetric. For sufficiently small curvatures the resulting field equations can be divided into two sets. One set, involving the antisymmetric part of the Ricci tensor $R_{\stackrel{\mu\nu}{\vee}}$, consists of the field equation for a massive vector field. The other set consists of the Einstein field equations with an energy momentum tensor for the vector field plus additional corrections. In a vacuum with $R_{\stackrel{\mu\nu}{\vee}}=0$ the field equations are shown to be the usual Einstein vacuum equations. This extends the universality of the vacuum Einstein equations, discussed by Ferraris et al. \cite{Fe1,Fe2}, to the Born-Infeld-Einstein action. In the simplest version of the theory there is a single coupling constant and by requiring that the Einstein field equations hold to a good approximation in neutron stars it is shown that mass of the vector field exceeds the lower bound on the mass of the photon. Thus, in this case the vector field cannot represent the electromagnetic field and would describe a new geometrical field. In a more general version in which the symmetric and antisymmetric parts of the Ricci tensor have different coupling constants it is possible to satisfy all of the observational constraints if the antisymmetric coupling is much larger than the symmetric coupling. In this case the antisymmetric part of the Ricci tensor can describe the electromagnetic field, although gauge invariance will be broken.Comment: 12 page

Testing the Unitarity of the CKM Matrix with a Space-Based Neutron Decay Experiment

If the Standard Model is correct, and fundamental fermions exist only in the three generations, then the CKM matrix should be unitary. However, there remains a question over a deviation from unitarity from the value of the neutron lifetime. We discuss a simple space-based experiment that, at an orbit height of 500 km above Earth, would measure the kinetic-energy, solid-angle, flux spectrum of gravitationally bound neutrons (kinetic energy K<0.606 eV at this altitude). The difference between the energy spectrum of neutrons that come up from the Earth's atmosphere and that of the undecayed neutrons that return back down to the Earth would yield a measurement of the neutron lifetime. This measurement would be free of the systematics of laboratory experiments. A package of mass $<25$ kg could provide a 10^{-3} precision in two years.Comment: 10 pages, 4 figures. Revised and updated for publicatio

Minimal Scalar Sector of 3-3-1 Models without Exotic Electric Charges

We study the minimal set of Higgs scalars, for models based on the local gauge group $SU(3)_c \otimes SU(3)_L \otimes U(1)_X$ which do not contain particles with exotic electric charges. We show that only two Higgs $SU(3)_L$ triplets are needed in order to properly break the symmetry. The exact tree-level scalar mass matrices resulting from symmetry breaking are calculated at the minimum of the most general scalar potential, and the gauge bosons are obtained, together with their couplings to the physical scalar fields. We show how the scalar sector introduced is enough to produce masses for fermions in a particular model which is an $E_6$ subgroup. By using experimental results we constrain the scale of new physics to be above 1.3 TeV.Comment: LaTeX, 22 pages, 1 figure include

Assembly of high nuclearity clusters from a family of tripodal tris-carboxylate ligands

A family of four tris-carboxylic acid ligands 1,3,5-tris(4′-carboxybiphenyl-2-yl)benzene (H3L1), 1,3,5-tris-2-carboxyphenylbenzene (H3L2), 1,3,5-tris(4″-carboxy-para-terphenyl-2-yl)benzene (H3L3) and 1,3,5-tris(3′-carboxybiphenyl-2-yl)benzene (H3L4) have been synthesised and reacted with first row transition metal cations to give nine complexes which have been structurally characterised by X-ray crystallography. The ligands share a common design motif having three arms connected to a benzene core via three ortho-disubstituted phenyl linkers. The ligands vary in length and direction of the carboxylic acid functionalised arms and are all able to adopt tripodal conformations in which the three arms are directed facially. The structures of [Zn8(μ4-O)(L1)4(HCO2)2(H2O)0.33(DMF)2] (1a-Zn), [Co14(L2)6((μ3-OH)8(HCO2)2(DMF)4(H2O)6] (2-Co), [Ni14(L2)6(μ3-OH)8(HCO2)2(DMF)4(H2O)6] (2-Ni), [Zn8(μ4-O)(L3)4(DMF)(H2O)4(NO3)2] (3-Zn), [Ni5(μ-OH)4(L2)2(H2O)6(DMF)4] (5-Ni), [Co8(μ4-O)4(L4)4(DMF)3(H2O)] (6-Co) and Fe3(μ3-O)(L4)2(H2O)(DMF)2)] (7-Fe) contain polynuclear clusters surrounded by ligands (L1–4)3− in tripodal conformations. The structure of [Zn2(HL1)2(DMF)4] (1b-Zn) shows it to be a binuclear complex in which the two ligands (HL2)2− are partially deprotonated whilst {[Zn3(L2)2(DMF)(H2O)(C5H5N)]·6(DMF)}n (4-Zn) is a 2D coordination network containing {Zn2(RCO2)4(solv)2} paddlewheel units. The conformations of the ligand arms in the complexes have been analysed, confirming that the shared ortho-disubstituted phenyl ring motif is a powerful and versatile tool for designing ligands able to form high-nuclearity coordination clusters when reacted with transition metal cations

Improved Spatial Resolution in Thick, Fully-Depleted CCDs withEnhanced Red Sensitivity

The point spread function (PSF) is an important measure of spatial resolution in CCDs for point-like objects, since it affects image quality and spectroscopic resolution. We present new data and theoretical developments for lateral charge diffusion in thick, fully-depleted charge-coupled devices (CCDs) developed at Lawrence Berkeley National Laboratory (LBNL). Because they can be over-depleted, the LBNL devices have no field-free region and diffusion is controlled through the application of an external bias voltage. We give results for a 3512 x 3512 format, 10.5 {micro}m pixel back-illuminated p-channel CCD developed for the SuperNova/Acceleration Probe (SNAP), a proposed satellite-based experiment designed to study dark energy. The PSF was measured at substrate bias voltages between 3 V and 115 V. At a bias voltage of 115 V, we measure an rms diffusion of 3.7 {+-} 0.2 {micro}m. Lateral charge diffusion in LBNL CCDs will meet the SNAP requirements

The Muon Anomalous Magnetic Moment: A Harbinger For "New Physics"

QED, Hadronic, and Electroweak Standard Model contributions to the muon anomalous magnetic moment, a_mu = (g_mu-2)/2, and their theoretical uncertainties are scrutinized. The status and implications of the recently reported 2.6 sigma experiment vs.theory deviation a_mu^{exp}-a_mu^{SM} = 426(165) times 10^{-11} are discussed. Possible explanations due to supersymmetric loop effects with m_{SUSY} \simeq 55 sqrt{tan beta} GeV, radiative mass mechanisms at the 1--2 TeV scale and other ``New Physics'' scenarios are examined.Comment: 24 page

TLR4 signaling augments B lymphocyte migration and overcomes the restriction that limits access to germinal center dark zones

B lymphocyte–intrinsic Toll-like receptor (TLR) signals amplify humoral immunity and can exacerbate autoimmune diseases. We identify a new mechanism by which TLR signals may contribute to autoimmunity and chronic inflammation. We show that TLR4 signaling enhances B lymphocyte trafficking into lymph nodes (LNs), induces B lymphocyte clustering and interactions within LN follicles, leads to sustained in vivo B cell proliferation, overcomes the restriction that limits the access of nonantigen-activated B cells to germinal center dark zones, and enhances the generation of memory and plasma cells. Intravital microscopy and in vivo tracking studies of B cells transferred to recipient mice revealed that TLR4-activated, but not nonstimulated, B cells accumulated within the dark zones of preexisting germinal centers even when transferred with antigen-specific B cells. The TLR4-activated cells persist much better than nonstimulated cells, expanding both within the memory and plasma cell compartments. TLR-mediated activation of B cells may help to feed and stabilize the spontaneous and ectopic germinal centers that are so commonly found in autoimmune individuals and that accompany chronic inflammation