Measurement of the Proteinase Inhibitors of the Bovine Pancreas by Radioimmunoassay

Bovine pancreas contains two polypeptide trypsin inhibitors that are not homologous and differ in their inhibitory activity towards chymotrypsin, kallikrein, elastase, and other serine proteinases. The Kunitz inhibitor and the Kazal inhibitor are present in approximately equimolar concentrations in bovine pancreatic tissue, yet only the Kazal inhibitor is detectable in the pancreatic juice. The Kazal inhibitor has been named the pancreatic secretory trypsin inhibitor, PSTI because its concentration in the pancreatic juice parallels that of the exocrine secretory proteins. The Kunitz inhibitor is considered the intracellular inhibitor, however, no direct information is available concerning the intracellular localization of these inhibitors in the pancreas. The preparation of /sup 125/I-labeled derivatives of Kazal and Kunitz inhibitors by the lactoperoxidase method and a radioimmunoassay for each inhibitor are described

Non-destructive imaging of an individual protein

The mode of action of proteins is to a large extent given by their ability to adopt different conformations. This is why imaging single biomolecules at atomic resolution is one of the ultimate goals of biophysics and structural biology. The existing protein database has emerged from X-ray crystallography, NMR or cryo-TEM investigations. However, these tools all require averaging over a large number of proteins and thus over different conformations. This of course results in the loss of structural information. Likewise it has been shown that even the emergent X-FEL technique will not get away without averaging over a large quantity of molecules. Here we report the first recordings of a protein at sub-nanometer resolution obtained from one individual ferritin by means of low-energy electron holography. One single protein could be imaged for an extended period of time without any sign of radiation damage. Since ferritin exhibits an iron core, the holographic reconstructions could also be cross-validated against TEM images of the very same molecule by imaging the iron cluster inside the molecule while the protein shell is decomposed

Exceptional type-I superconductivity of the layered silver oxide Ag5_5Pb2_2O6_6

We report zero-resistivity transition and the details of magnetic transition of a layered silver oxide Ag$_5$Pb$_2$O$_6$ single crystal, which make definitive evidence of superconductivity in this compound. In the AC susceptibility of a mono-crystal, we observed large supercooling, as well as positive peaks in the real part of the susceptibility indicating the reversibility of magnetic process. These observations reveal that Ag$_5$Pb$_2$O$_6$ is probably the first oxide that shows type-I superconductivity. Evaluation of the superconducting parameters not only gives confirming evidence of type-I superconductivity, but also indicates that it is a dirty-limit superconductor. We also analyze supercooling to determine the upper limit of the Ginzburg-Landau parameter.Comment: v2: PACS numbers are adde

A qubit strongly-coupled to a resonant cavity: asymmetry of the spontaneous emission spectrum beyond the rotating wave approximation

We investigate the spontaneous emission spectrum of a qubit in a lossy resonant cavity. We use neither the rotating-wave approximation nor the Markov approximation. The qubit-cavity coupling strength is varied from weak, to strong, even to lower bound of the ultra-strong. For the weak-coupling case, the spontaneous emission spectrum of the qubit is a single peak, with its location depending on the spectral density of the qubit environment. Increasing the qubit-cavity coupling increases the asymmetry (the positions about the qubit energy spacing and heights of the two peaks) of the two spontaneous emission peaks (which are related to the vacuum Rabi splitting) more. Explicitly, for a qubit in a low-frequency intrinsic bath, the height asymmetry of the splitting peaks becomes larger, when the qubit-cavity coupling strength is increased. However, for a qubit in an Ohmic bath, the height asymmetry of the spectral peaks is inverted from the same case of the low-frequency bath, when the qubit is strongly coupled to the cavity. Increasing the qubit-cavity coupling to the lower bound of the ultra-strong regime, the height asymmetry of the left and right peak heights are inverted, which is consistent with the same case of low-frequency bath, only relatively weak. Therefore, our results explicitly show how the height asymmetry in the spontaneous emission spectrum peaks depends not only on the qubit-cavity coupling, but also on the type of intrinsic noise experienced by the qubit.Comment: 10pages, 5 figure

Reduction and analysis of photometric data on Comet Halley

The discovery that periodic variations in the brightness of Comet Halley were characterized by two unrelated frequencies implies that the nucleus is in a complex state of rotation. It either nutates as a result of the random addition of small torque perturbations accumulated over many perihelion passages, or the jet activity torques are so strong that it precesses wildly at each perihelion passage. To diagnose the state of nuclear rotation, researchers began a program to acquire photometric time series of the comet as it recedes from the sun. The intention is to observe the decay of the comet's atmosphere and then, when it is unemcumbered by the light of the coma, follow the light variation of the nucleus itself. The latter will be compared with preperihelion time series and the orientation of the nucleus at the time of Vega and Giotto flybys and an accurate rotational ephemeris constructed. Halley was observed on 38 nights during 1987 and approximately 21 nights in 1988. The comet moved from 5 AU to 8.5 AU during this time. The brightness of the coma was found to rapidly decrease in 1988 as the coma and cometary activity collapses. The magnitude in April 1988 was 19 mag (visual) and it is predicted that the nucleus itself will be the major contributor to the brightness in the 1988 and 1989 season

Multi-Modal Human-Machine Communication for Instructing Robot Grasping Tasks

A major challenge for the realization of intelligent robots is to supply them with cognitive abilities in order to allow ordinary users to program them easily and intuitively. One way of such programming is teaching work tasks by interactive demonstration. To make this effective and convenient for the user, the machine must be capable to establish a common focus of attention and be able to use and integrate spoken instructions, visual perceptions, and non-verbal clues like gestural commands. We report progress in building a hybrid architecture that combines statistical methods, neural networks, and finite state machines into an integrated system for instructing grasping tasks by man-machine interaction. The system combines the GRAVIS-robot for visual attention and gestural instruction with an intelligent interface for speech recognition and linguistic interpretation, and an modality fusion module to allow multi-modal task-oriented man-machine communication with respect to dextrous robot manipulation of objects.Comment: 7 pages, 8 figure

Solution to the twin image problem in holography

While the invention of holography by Dennis Gabor truly constitutes an ingenious concept, it has ever since been troubled by the so called twin image problem limiting the information that can be obtained from a holographic record. Due to symmetry reasons there are always two images appearing in the reconstruction process. Thus, the reconstructed object is obscured by its unwanted out of focus twin image. Especially for emission electron as well as for x- and gamma-ray holography, where the source-object distances are small, the reconstructed images of atoms are very close to their twin images from which they can hardly be distinguished. In some particular instances only, experimental efforts could remove the twin images. More recently, numerical methods to diminish the effect of the twin image have been proposed but are limited to purely absorbing objects failing to account for phase shifts caused by the object. Here we show a universal method to reconstruct a hologram completely free of twin images disturbance while no assumptions about the object need to be imposed. Both, amplitude and true phase distributions are retrieved without distortion

Transition from a Tomonaga-Luttinger liquid to a Fermi liquid in potassium intercalated bundles of single wall carbon nanotubes

We report on the first direct observation of a transition from a Tomonaga-Luttinger liquid to a Fermi liquid behavior in potassium intercalated mats of single wall carbon nanotubes (SWCNT). Using high resolution photoemission spectroscopy an analysis of the spectral shape near the Fermi level reveals a Tomonaga-Luttinger liquid power law scaling in the density of states for the pristine sample and for low dopant concentration. As soon as the doping is high enough to fill bands of the semiconducting tubes a distinct transition to a bundle of only metallic SWCNT with a scaling behavior of a normal Fermi liquid occurs. This can be explained by a strong screening of the Coulomb interaction between charge carriers and/or an increased hopping matrix element between the tubes.Comment: 5 pages, 4 figure