Microwave diode amplifiers with low intermodulation distortion

Distortions can be greatly reduced in narrow-band applications by using the second harmonic. The ac behavior of simplified diode amplifier has negative resistance depending on slope of equivalent I-V curve

Image retrieval by hypertext links

This paper presents a model for retrieval of images from a large World Wide Web based collection. Rather than considering complex visual recognition algorithms, the model presented is based on combining evidence of the text content and hypertext structure of the Web. The paper shows that certain types of query are amply served by this form of representation. It also presents a novel means of gathering relevance judgements

Cavity QED determination of atomic number statistics in optical lattices

We study the reflection of two counter-propagating modes of the light field in a ring resonator by ultracold atoms either in the Mott insulator state or in the superfluid state of an optical lattice. We obtain exact numerical results for a simple two-well model and carry out statistical calculations appropriate for the full lattice case. We find that the dynamics of the reflected light strongly depends on both the lattice spacing and the state of the matter-wave field. Depending on the lattice spacing, the light field is sensitive to various density-density correlation functions of the atoms. The light field and the atoms become strongly entangled if the latter are in a superfluid state, in which case the photon statistics typically exhibit complicated multimodal structures.Comment: 10 pages revtex, 13 figure

Science is perception: what can our sense of smell tell us about ourselves and the world around us?

Human sensory processes are well understood: hearing, seeing, perhaps even tasting and touch—but we do not understand smell—the elusive sense. That is, for the others we know what stimuli causes what response, and why and how. These fundamental questions are not answered within the sphere of smell science; we do not know what it is about a molecule that … smells. I report, here, the status quo theories for olfaction, highlighting what we do not know, and explaining why dismissing the perception of the input as ‘too subjective’ acts as a roadblock not conducive to scientific inquiry. I outline the current and new theory that conjectures a mechanism for signal transduction based on quantum mechanical phenomena, dubbed the ‘swipe card’, which is perhaps controversial but feasible. I show that such lines of thinking may answer some questions, or at least pose the right questions. Most importantly, I draw links and comparisons as to how better understanding of how small (10’s of atoms) molecules can interact so specially with large (10 000’s of atoms) proteins in a way that is so integral to healthy living. Repercussions of this work are not just important in understanding a basic scientific tool used by us all, but often taken for granted, it is also a step closer to understanding generic mechanisms between drug and receptor, for example

The development of a cislunar space infrastructure

The primary objective of this Advanced Mission Design Program is to define the general characteristics and phased evolution of a near-Earth space infrastructure. The envisioned foundation includes a permanently manned, self-sustaining base on the lunar surface, a space station at the Libration Point between earth and the moon (L1), and a transportation system that anchors these elements to the Low Earth Orbit (LEO) station. The implementation of this conceptual design was carried out with the idea that the infrastructure is an important step in a larger plan to expand man's capabilities in space science and technology. Such expansion depends on low cost, reliable, and frequent access to space for those who wish to use the multiple benefits of this environment. The presence of a cislunar space infrastructure would greatly facilitate the staging of future planetary missions, as well as the full exploration of the lunar potential for science and industry. The rationale for, and a proposed detailed scenario in support of, the cislunar space infrastructure are discussed

Electromagnetic Transition Strengths in Heavy Nuclei

We calculate reduced B(E2) and B(M1) electromagnetic transition strengths within and between K-bands in support of a recently proposed model for the structure of heavy nuclei. Previously, only spectra and a rough indication of the largest B(E2) strengths were reported. The present more detailed calculations should aid the experimental identification of the predicted $0^+$, $1^+$ and $2^+$ bands and, in particular, act to confirm or refute the suggestion that the model $0^+$ and $2^+$ bands correspond to the well known and widespread beta and gamma bands. Furthermore they pinpoint transitions which can indicate the presence of a so far elusive $1^+$ band by feeding relatively strongly into or out of it. Some of these transitions may already have been measured in $^{230}$Th, $^{232}$Th and $^{238}$U.Comment: 10 pages, 1 Figure, submitted to Physical Review

Prototype scintillator cell for an In-based solar neutrino detector

We describe the work carried out at MPIK to design, model, build and characterize a prototype cell filled with a novel indium-loaded scintillator of interest for real-time low energy solar neutrino spectroscopy. First, light propagation in optical modules was studied with experiments and Monte Carlo simulations. Subsequently a 5 cm x 5 cm x 100 cm prototype detector was set up and the optical performances of several samples were measured. We first tested a benchmark PXE-based scintillator, which performed an attenuation length of ~ 4.2 m and a photo-electron yield of ~ 730 pe/MeV. Then we measured three In-loaded samples. At an In-loading of 44 g/l, an energy resolution of ~ 11.6 % and a spatial resolution of ~ 7 cm were attained for 477 keV recoil electrons. The long-range attenuation length in the cell was ~1.3 m and the estimated photo-electron yield ~ 200 pe/MeV. Light attenuation and relative light output of all tested samples could be reproduced reasonably well by MC. All optical properties of this system have remained stable over a period of > 1 y.Comment: 57 pages, 19 figures, 10 tables elsevier template for manuscript submission submitted to NIMA 10 February 200

Using Birdsfoot Trefoil in Kentucky Pastures

Birdsfoot trefoil (Lotus corniculatus L.) is an excellent pasture legume in the Corn Belt and in northeast United states . It has usually been considered too poorly adapted to Kentucky to merit trial by the farmers. Observations and grazing results in Woodford county during the last 14 years, however, indicate that this view is no longer valid. A grazing trial was established in 1954, with birdsfoot trefoil and Kentucky bluegrass as one of three mixtures used. Trefoil was seeded alone in the spring, and an excellent stand was obtained. Bluegrass was drilled in the established trefoil in September 1954. There were four 4-acre experimental pastures of trefoil-bluegrass and an additional 6-acre field which was used as a reserve pasture

Characterization of Knots and Links Arising From Site-specific Recombination on Twist Knots

We develop a model characterizing all possible knots and links arising from recombination starting with a twist knot substrate, extending previous work of Buck and Flapan. We show that all knot or link products fall into three well-understood families of knots and links, and prove that given a positive integer $n$, the number of product knots and links with minimal crossing number equal to $n$ grows proportionally to $n^5$. In the (common) case of twist knot substrates whose products have minimal crossing number one more than the substrate, we prove that the types of products are tightly prescribed. Finally, we give two simple examples to illustrate how this model can help determine previously uncharacterized experimental data.Comment: 32 pages, 7 tables, 27 figures, revised: figures re-arranged, and minor corrections. To appear in Journal of Physics

Clarification of the relationship between bound and scattering states in quantum mechanics: Application to 12C + alpha

Using phase-equivalent supersymmetric partner potentials, a general result from the inverse problem in quantum scattering theory is illustrated, i.e., that bound-state properties cannot be extracted from the phase shifts of a single partial wave, as a matter of principle. In particular, recent R-matrix analyses of the 12C + alpha system, extracting the asymptotic normalization constant of the 2+ subthreshold state, C12, from the l=2 elastic-scattering phase shifts and bound-state energy, are shown to be unreliable. In contrast, this important constant in nuclear astrophysics can be deduced from the simultaneous analysis of the l=0, 2, 4, 6 partial waves in a simplified potential model. A new supersymmetric inversion potential and existing models give C12=144500+-8500 fm-1/2.Comment: Expanded version (50% larger); three errors corrected (conversion of published reduced widths to ANCs); nine references added, one remove