19,783 research outputs found
Voluntary presetting of the vestibular ocular reflex permits gaze stabilization despite perturbation of fast head movements
Normal subjects are able to change voluntarily and continuously their head-eye latency together with their compensatory eye movement gain. A continuous spectrum of intent-latency modes of the subject's coordinated gaze through verbal feedback could be demonstrated. It was also demonstrated that the intent to counteract any perturbation of head-eye movement, i.e., the mental set, permitted the subjects to manipulate consciously their vestibular ocular reflex (VOR) gain. From the data, it is inferred that the VOR is always on. It may be, however, variably suppressed by higher cortical control. With appropriate training, head-mounted displays should permit an easy VOR presetting that leads to image stabilization, perhaps together with a decrease of possible misjudgements
Isolation and Characterization of a Cellular Protein-Lipid Complex from Ascites Fluid Caused by Various Neoplasms
High concentrations of lipids in ascites fluid caused by peritoneal carcinomatosis have been described recently. Since their nature has not yet been clarified, we isolated ascitic lipids from 25 patients with various neoplasms for further characterization. After chromatography on Sephadex G-100 gels, the ascitic lipids were fractionated on a Biogel A-5m column in three peaks. The second and third peaks were identified as low and high density lipoproteins, which were most likely of plasmatic origin, and represented the major amounts of ascitic lipids. The first peak was eluted in the void volume, indicating a molecular weight over 5 million. It consisted, on the average, of 65.3% protein, 16.2% triglycerides, 7.4% phospholipids, and 7.0% cholesterol. In a CsCl gradient, this protein-lipid complex floated in the density range from 1.128 to 1.181 g/ml. Sodium dodecyl sulfate: polyacrylamide gel electrophoresis separated up to 11 protein subunits (Mr 29,000 to 97,000), and electron microscopy revealed globular particles of 36 to 64 nm in diameter. The macromolecular complex showed no immunological reaction against anti-{alpha}- and anti-ß-lipoproteins, but a single precipitation line against anti-liver-specific lipoprotein was seen.
The biochemical characteristics of this protein-lipid complex proved to have a close relationship to liver-specific lipoprotein. It is most likely derived from cell membranes of the peritoneum detached by carcinomatosis
Carrier induced ferromagnetism in diluted local-moment systems
The electronic and magnetic properties of concentrated and diluted
ferromagnetic semiconductors are investigated by using the Kondo lattice model,
which describes an interband exchange coupling between itinerant conduction
electrons and localized magnetic moments. In our calculations, the electronic
problem and the local magnetic problem are solved separately. For the
electronic part an interpolating self-energy approach together with a coherent
potential approximation (CPA) treatment of a dynamical alloy analogy is used to
calculate temperature-dependent quasiparticle densities of states and the
electronic self-energy of the diluted local-moment system. For constructing the
magnetic phase diagram we use a modified RKKY theory by mapping the interband
exchange to an effective Heisenberg model. The exchange integrals appear as
functionals of the diluted electronic self-energy being therefore temperature-
and carrier-concentration-dependent and covering RKKY as well as double
exchange behavior. The disorder of the localized moments in the effective
Heisenberg model is solved by a generalized locator CPA approach. The main
results are: 1) extremely low carrier concentrations are sufficient to induce
ferromagnetism; 2) the Curie temperature exhibits a strikingly non-monotonic
behavior as a function of carrier concentration with a distinct maximum; 3)
curves break down at critical due to antiferromagnetic correlations
and 4) the dilution always lowers but broadens the ferromagnetic region
with respect to carrier concentration.Comment: 11 pages, 5 figure
Diffuse LEED intensities of disordered crystal surfaces : II. Multiple scattering on disordered overlayers
The diffraction of low energy electrons from disordered overlayers adsorbed on ordered substrates is treated theoretically by an extension of Beeby's multiple scattering method. A lattice gas model is assumed for the disordered adsorbate layer. Multiple scattering within a certain area around each atom — each atom of the overlayer and within the ordered substrate — is treated self-consistently, the remaining contributions to the total scattering amplitude being averaged. The theory can be used in the limiting cases of random distribution and of long range order within the adsorbate layer
Diffuse LEED intensities of disordered crystal surfaces : IV. Application of the disorder theory
The principles of the statistical disorder theory are discussed briefly. The theory is applied to a model of the disordered (101)Au surface with the characteristic (1 × 2) supersstructure. A fit procedure is described, by which the experimental angular intensity profiles are used directly to determine the disorder parameters and the interaction energies between the chains of surface atoms
Diffuse LEED intensities of disordered crystal surfaces : I. Correlations between statistics and multiple diffraction
It is shown that the diffraction of slow electrons from disordered crystal surfaces is correlated with the problem of thermodynamical statistics. The correlation functions are completely determined by the self-energies and interaction energies of neighboring complexes. These quantities solve the problem of a-priori probabilities and the cooperative phenomenon of correlation functions of these complexes. If the calculation of a certain set of multiple scattering amplitudes is possible, the remaining problem of determining the diffuse LEED pattern becomes solvable. The calculation of angular beam profiles follows the same lines as already described for the kinematic theory of X-ray diffraction
On Throughput Maximization of Grant-Free Access with Reliability-Latency Constraints
Enabling autonomous driving and industrial automation with wireless networks
poses many challenges, which are typically abstracted through reliability and
latency requirements. One of the main contributors to latency in cellular
networks is the reservation-based access, which involves lengthy and
resource-inefficient signaling exchanges. An alternative is to use grant-free
access, in which there is no resource reservation. A handful of recent works
investigated how to fulfill reliability and latency requirements with different
flavors of grant-free solutions. However, the resource efficiency, i.e., the
throughput, has been only the secondary focus. In this work, we formulate the
throughput of grant-free access under reliability-latency constraints, when the
actual number of arrived users or only the arrival distribution are known. We
investigate how these different levels of knowledge about the arrival process
influence throughput performance of framed slotted ALOHA with -multipacket
reception, for the Poisson and Beta arrivals. We show that the throughput under
reliability-latency requirements can be significantly improved for the higher
expected load of the access network, if the actual number of arrived users is
known. This insight motivates the use of techniques for the estimation of the
number of arrived users, as this knowledge is not readily available in
grant-free access. We also asses the impact of estimation error, showing that
for high reliability-latency requirements the gains in throughput are still
considerable.Comment: Accepted for publication in ICC'201
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