3,235 research outputs found
Experience applicable to the Viking lander from a study of related space flight projects
Related space mission data for baseline evaluation of Viking Lander design and operatio
Statistical mechanics of temporal association in neural networks with transmission delays
We study the representation of static patterns and temporal sequences in neural networks with signal delays and a stochastic parallel dynamics. For a wide class of delay distributions, the asymptotic network behavior can be described by a generalized Gibbs distribution, generated by a novel Lyapunov functional for the determination dynamics. We extend techniques of equilibrium statistical mechanics so as to deal with time-dependent phenomena, derive analytic results for both retrieval quality and storage capacity, and compare them with numerical simulations
Demonstration and characterization of α-human atrial natriuretic factor in human plasma
AbstractThis paper describes a highly specific and sensitive radioimmunoassay for α-human atrial natriuretic factor (α-hANF), the C-terminal 28-amino-acid residue portion of human prepro-ANF in human plasma. A novel extraction and prepurification procedure allowed for detection of levels of immunoreactive-α-hANF as low as 0.5 fmolml. In normotensive subjects, levels in the range 1–23 fmolml (mean = 8.9 fmolml) were found. Combined gel permeation and HPLC analysis demonstrated that this ir-α-hANF was comprised virtually exclusively of authentic 28-residue β-hANF. No evidence for occurrence of larger precursor forms in human plasma was acquired. A heterogenous group of hypertensive patients displayed considerably higher levels (mean = 62.2 fmolml), of interest in view of the hypotensive properties of ANF.Atrial natriuretic factorHuman plasmaExtractionChromatographie characterizationHypertensio
Distances sets that are a shift of the integers and Fourier basis for planar convex sets
The aim of this paper is to prove that if a planar set has a difference
set satisfying for suitable than
has at most 3 elements. This result is motivated by the conjecture that the
disk has not more than 3 orthogonal exponentials. Further, we prove that if
is a set of exponentials mutually orthogonal with respect to any symmetric
convex set in the plane with a smooth boundary and everywhere non-vanishing
curvature, then # (A \cap {[-q,q]}^2) \leq C(K) q where is a constant
depending only on . This extends and clarifies in the plane the result of
Iosevich and Rudnev. As a corollary, we obtain the result from \cite{IKP01} and
\cite{IKT01} that if is a centrally symmetric convex body with a smooth
boundary and non-vanishing curvature, then does not possess an
orthogonal basis of exponentials
Harmonic lattice behavior of two-dimensional colloidal crystals
Using positional data from video-microscopy and applying the equipartition
theorem for harmonic Hamiltonians, we determine the wave-vector-dependent
normal mode spring constants of a two-dimensional colloidal model crystal and
compare the measured band-structure to predictions of the harmonic lattice
theory. We find good agreement for both the transversal and the longitudinal
mode. For , the measured spring constants are consistent with the
elastic moduli of the crystal.Comment: 4 pages, 3 figures, submitte
Collection of relevant results obtained with the Skylab images by the Institute for Space Research, INPE
There are no author-identified significant results in this report
Lorentz angle measurements in irradiated silicon detectors between 77 K and 300 K
Future experiments are using silicon detectors in a high radiation
environment and in high magnetic fields. The radiation tolerance of silicon
improves by cooling it to temperatures below 180 K. At low temperatures the
mobility increases, which leads to larger deflections of the charge carriers by
the Lorentz force. A good knowledge of the Lorentz angle is needed for design
and operation of silicon detectors. We present measurements of the Lorentz
angle between 77 K and 300 K before and after irradiation with a primary beam
of 21 MeV protons.Comment: 13 pages, 9 figures, submitted to ICHEP2000, Osaka, Japa
Jacobi structures revisited
Jacobi algebroids, that is graded Lie brackets on the Grassmann algebra
associated with a vector bundle which satisfy a property similar to that of the
Jacobi brackets, are introduced. They turn out to be equivalent to generalized
Lie algebroids in the sense of Iglesias and Marrero and can be viewed also as
odd Jacobi brackets on the supermanifolds associated with the vector bundles.
Jacobi bialgebroids are defined in the same manner. A lifting procedure of
elements of this Grassmann algebra to multivector fields on the total space of
the vector bundle which preserves the corresponding brackets is developed. This
gives the possibility of associating canonically a Lie algebroid with any local
Lie algebra in the sense of Kirillov.Comment: 20 page
Electron scattering in atomic force microscopy experiments
It has been shown that electron transitions, as measured in a scanning
tunnelling microscope (STM), are related to chemical interactions in a
tunnelling barrier. Here, we show that the shape and apparent height of
subatomic features in an atomic force microscopy (AFM) experiment on Si(111)
depend directly on the available electron states of the silicon surface and the
silicon AFM tip. Simulations and experiments confirm that forces and currents
show similar subatomic variations for tip-sample distances approaching the bulk
bonding length.Comment: 5 pages and 4 figure
Farmers’ management of functional biodiversity goes beyond pest management in organic European apple orchards
Supporting functional biodiversity (FB), which provides natural pest regulation, is an environmentally sound and promising approach to reduce pesticide use in perennial cultures such as apple, especially in organic farming. However, little is known about farmers’ practices and motivations to implement techniques that favor FB, especially whether or not they really expect anything from FB in terms of pest regulation. In fact, FB-supporting techniques (FB-techniques) are massively questioned by practitioners due to inadequate information about their effectiveness. An interview survey was performed in eight European countries(i) to describe farmers’ practices and identify promising FB-techniques: (ii) to better understand their perceptions of and values associated with FB; and (iii) to identify potential drivers of (non-)adoption. Fifty-five advisors and 125 orchard managers with various degrees of experience and convictions about FB were interviewed and a total of 24 different FB-techniques which can be assigned to three different categories (ecological infrastructures, farming practices and redesign techniques) were described. Some were well-established measures (e.g., hedges and bird houses), while others were more marginal and more recent (e.g., animal introduction and compost). On average, farmers combined more than four techniques that had been implemented over a period of 13 years, especially during their establishment or conversion period. In general, it was difficult for farmers to evaluate the effectiveness of individual FB-techniques on pest regulation. They considered FB-techniques as a whole, targeting multiple species, and valued multiple ecosystem services in addition to pest regulation. The techniques implemented and their associated values differed among farmers who adopted various approaches towards FB. Three different approaches were defined: passive, active and integrated. Their appraisal of FB is even more complex because it may change with time and experience. These findings provide empirical evidence that the practical implementation of promising techniques remains a challenge, considering the diversity of situations and evaluation criteria. Increased cooperation between researchers, farmers and advisors should more effectively target research, advisory support and communication to meet farmers’ needs and perceptions
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