484 research outputs found
Investigations on alternative substances for control of apple scab - results from sanitation trials
The intention of this research project, which was supported within the "Bundesprogramm Ökologischer
Landbau", was to look for alternatives in organic fruit growing to control apple scab, Venturia
inaequalis. One important part of the investigations was the application of different substances like
microbiological nutrient media, enzymes usually used for production of fruit juices and organic fertilizers
on their effect on the ascospore potential on depots of fallen leaves. Some substances like
TRYPTIC SOY BROTH increased the decomposition of the leaves significantly, other like BACTOFIL B
and HUMOFIX showed nearly no effect on the decomposition, but reduced the ascospore potential in
early spring by 80 % compared to the untreated control
Conduction Channels of One-Atom Zinc Contacts
We have determined the transmission coefficients of atomic-sized Zn contacts
using a new type of breakjunction which contains a whisker as a central bridge.
We find that in the last conductance plateau the transport is unexpectedly
dominated by a well-transmitting single conduction channel. We explain the
experimental findings with the help of a tight-binding model which shows that
in an one-atom Zn contact the current proceeds through the 4s and 4p orbitals
of the central atom.Comment: revtex4, 5 pages, 5 figure
Machine learning based activity recognition to identify wasteful activities in production
Lean Management focusses on the elimination of wasteful activities in production. Whilst numerous methods such as value stream analysis or spaghetti diagrams exist to identify transport, inventory, defects, overproduction or waiting, the waste of human motion is difficult to detect. Activity recognition attempts to categorize human activities using sensor data. Human activity recognition (HAR) is already used in the consumer domain to detect human activities such as walking, climbing stairs or running. This paper presents an approach to transfer the human activity recognition methods to production in order to detect wasteful motion in production processes and to evaluate workplaces. Using sensor data from ordinary smartphones, long-term short-term memory networks (LSTM) are used to classify human activities. Additional to the LSTM-network, the paper contributes a labeled data set for supervised learning. The paper demonstrates how activity recognition can be included in learning factory training starting from the generation of training data to the analysis of the results
Electron-vibration interaction in transport through atomic gold wires
We calculate the effect of electron-vibration coupling on conduction through
atomic gold wires, which was measured in the experiments of Agra\"it et al.
[Phys. Rev. Lett. 88, 216803 (2002)]. The vibrational modes, the coupling
constants, and the inelastic transport are all calculated using a tight-binding
parametrization and the non-equilibrium Green function formalism. The
electron-vibration coupling gives rise to small drops in the conductance at
voltages corresponding to energies of some of the vibrational modes. We study
systematically how the position and height of these steps vary as a linear wire
is stretched and more atoms are added to it, and find a good agreement with the
experiments. We also consider two different types of geometries, which are
found to yield qualitatively similar results. In contrast to previous
calculations, we find that typically there are several close-lying drops due to
different longitudinal modes. In the experiments, only a single drop is usually
visible, but its width is too large to be accounted for by temperature.
Therefore, to explain the experimental results, we find it necessary to
introduce a finite broadening to the vibrational modes, which makes the
separate drops merge into a single, wide one. In addition, we predict how the
signatures of vibrational modes in the conductance curves differ between linear
and zigzag-type wires.Comment: 19 pages, 12 figure
Decay of the Maxwell field on the Schwarzschild manifold
We study solutions of the decoupled Maxwell equations in the exterior region
of a Schwarzschild black hole. In stationary regions, where the Schwarzschild
coordinate ranges over , we obtain a decay rate of
for all components of the Maxwell field. We use vector field methods
and do not require a spherical harmonic decomposition.
In outgoing regions, where the Regge-Wheeler tortoise coordinate is large,
, we obtain decay for the null components with rates of
, , and . Along the event horizon and in ingoing regions, where ,
and when , all components (normalized with respect to an ingoing null
basis) decay at a rate of C \uout^{-1} with \uout=t+r_* in the exterior
region.Comment: 37 pages, 5 figure
Metallic properties of magnesium point contacts
We present an experimental and theoretical study of the conductance and
stability of Mg atomic-sized contacts. Using Mechanically Controllable Break
Junctions (MCBJ), we have observed that the room temperature conductance
histograms exhibit a series of peaks, which suggests the existence of a shell
effect. Its periodicity, however, cannot be simply explained in terms of either
an atomic or electronic shell effect. We have also found that at room
temperature, contacts of the diameter of a single atom are absent. A possible
interpretation could be the occurrence of a metal-to-insulator transition as
the contact radius is reduced, in analogy with what it is known in the context
of Mg clusters. However, our first principle calculations show that while an
infinite linear chain can be insulating, Mg wires with larger atomic
coordinations, as in realistic atomic contacts, are alwaysmetallic. Finally, at
liquid helium temperature our measurements show that the conductance histogram
is dominated by a pronounced peak at the quantum of conductance. This is in
good agreement with our calculations based on a tight-binding model that
indicate that the conductance of a Mg one-atom contact is dominated by a single
fully open conduction channel.Comment: 14 pages, 5 figure
Local energy decay of massive Dirac fields in the 5D Myers-Perry metric
We consider massive Dirac fields evolving in the exterior region of a
5-dimensional Myers-Perry black hole and study their propagation properties.
Our main result states that the local energy of such fields decays in a weak
sense at late times. We obtain this result in two steps: first, using the
separability of the Dirac equation, we prove the absence of a pure point
spectrum for the corresponding Dirac operator; second, using a new form of the
equation adapted to the local rotations of the black hole, we show by a Mourre
theory argument that the spectrum is absolutely continuous. This leads directly
to our main result.Comment: 40 page
Theoretical analysis of the conductance histograms and structural properties of Ag, Pt and Ni nanocontacts
Conductance histograms are a valuable tool to study the intrinsic conduction
properties of metallic atomic-sized contacts. These histograms show a peak
structure, which is characteristic of the type of metal under investigation.
Despite the enormous progress in the understanding of the electronic transport
in metallic nanowires, the origin of this peak structure is still a basic open
problem. In the present work we tackle this issue, extending our theoretical
analysis of Au conductance histograms [Dreher et al., PRB 72, 075435 (2005)] to
different types of metals, namely, Ag, Pt and ferromagnetic Ni. We combine
classical molecular dynamics simulations of the breaking of nanocontacts with
conductance calculations based on a tight-binding model. This combination gives
us access to crucial information such as contact geometries, strain forces,
minimum cross-sections, the conductance, transmissions of the individual
conduction channels and, in the case of Ni, the spin polarization of the
current. We shall also briefly discuss investigations of Al atomic-sized
contacts. From our analysis we conclude that the differences in the histograms
of these metals are due to (i) the very different electronic structures, which
means different atomic orbitals contributing to the transport, and (ii) the
different mechanical properties, which in a case like Pt lead to the formation
of special structures, namely monoatomic chains. Of particular interest are
results for Ni that indicate the absence of any conductance quantization, and
show how the current polarization evolves (including large fluctuations) from
negative values in thick contacts to even positive values in the tunneling
regime after rupture of the contact. Finally, we also present a detailed
analysis of the breaking forces of these metallic contacts.Comment: 22 pages, 19 figure
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