Search Results - (Author, Cooperation:Krafft)

Krafft, Fritz

Unknown

216 S.

German

2019-08-28

Algorithmische Entscheidungssysteme werden immer häufiger zur Klassifikation und Prognose von menschlichem Verhalten herangezogen. Hierbei gibt es einen breiten Diskurs um die Messung der Entscheidungsqualität solcher Systeme (Qualität) und die mögliche Diskriminierung von Teilgruppen (Fairness), welchen sich dieser Artikel widmet. Wir zeigen auf, dass es miteinander unvereinbare Fairnessmaße gibt, wobei wir auf zwei im Speziellen eingehen. Für sich allein betrachtet sind die zwei Maße zwar logisch und haben je nach Anwendungsgebiet auch ihre Daseinsberechtigung, jedoch können nicht beide zugleich erfüllt werden. Somit zeigt sich, dass gerade im Einsatz algorithmischer Entscheidungssysteme im Bereich der öffentlichen IT aufgrund ihres großen Wirkungsbereichs auf das Gemein-wohl höchste Vorsicht bei der Wahl solcher Maßstäbe herrschen muss. Wird im Anwendungsfall die Erfüllung sich widersprechender Maßstäbe gefordert, so muss darüber nachgedacht werden, ob eine algorithmische Lösung an dieser Stelle überhaupt eingesetzt werden darf.

Technik, Technologie ; Naturwissenschaften ; Technology (Applied sciences) ; Science ; Technikfolgenabschätzung ; Naturwissenschaften, Technik(wissenschaften), angewandte Wissenschaften ; Technology Assessment ; Natural Science and Engineering, Applied Sciences ; Algorithmus ; Entscheidungsfindung ; Verhaltensprognose ; Diskriminierung ; Fairness ; Bewertung ; algorithm ; decision making ; behavior prognosis ; discrimination ; fairness ; evaluation ; 50200 ; 20800

Sammelwerksbeitrag, collection article

2019-08-28

Zunehmend treffen algorithmische Entscheidungssysteme (ADM-Systeme) Entscheidungen über Menschen und beeinflussen damit öffentliche Räume oder die gesellschaftlichen Teilhabemöglichkeiten von Individuen; damit gehören derartige Systeme zur öffentlichen IT. Hier zeigen wir, am Beispiel der Analyse von Rückfälligkeitsvorhersagesystemen und dem Datenspende-Projekt zur Bundestagswahl 2017, wie solche Systeme mit Hilfe von Black-Box-Analysen von der Öffentlichkeit untersucht werden können und wo die Grenzen dieses Ansatzes liegen. Insbesondere bei ADM-Systemen der öffentlichen Hand zeigt sich hierbei, dass eine Black-Box-Analyse nicht ausreichend ist, sondern hier ein qualitätsgesicherter Prozess der Entwicklung und Evaluation solcher Systeme notwendig ist.

Technik, Technologie ; Technology (Applied sciences) ; Algorithmisches Entscheidungssystem; Algorithmic Decision Making System; ADM-System ; Technikfolgenabschätzung ; Technology Assessment ; Algorithmus ; Automatisierung ; Bundesrepublik Deutschland ; Digitalisierung ; Entscheidungsfindung ; Entscheidungsprozess ; Personalisierung ; Suchmaschine ; Soziale Medien ; Prognoseverfahren ; Transparenz ; Verhaltensprognose ; soziales Problem ; algorithm ; automation ; Federal Republic of Germany ; digitalization ; decision making ; decision making process ; personalization ; search engine ; social media ; forecast procedure ; transparency ; behavior prognosis ; social problem ; 50200 ; 20800

Sammelwerksbeitrag, collection article

1089-7550

AIP Digital Archive

Physics

A wideband microwave absorption spectrometer with a coplanar waveguide transmission line was used to characterize the magnetic field dependence of microwave absorption in high temperature superconductors. This technique is useful for the nondestructive evaluation of high temperature superconductor bulk and thin film samples prior to their application in microwave devices and sensors. Results are presented for various types and forms of samples including bulk YBCO, laser-ablated thin film YBCO, and Ag-doped YBCO wire.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Heretofore, vector Preisach models have consisted of angularly distributed scalar models. We postulate adding rotational capability to the binary response of the Preisach elements to obtain vector behavior using a single density function. A rotating field H divides the Preisach density function, which is obtained from scalar measurements, into regions associated with magnetization directions dependent on the applied field history. The magnetizations of elements with h*〈||H||, where h* is the larger of the switching field magnitudes, follow exactly the direction of the rotating field. Those with h*〉α||H|| (1〈α〈2 and is experimentally determined) are not oriented by H, but may be switched by the parallel component of H. Elements with intermediate values of h* rotate irreversibly at an angle which lags the field. The model has the same scalar properties in all directions and has performed well in simulating measurements made on a barium ferrite floppy disk with a vector vibrating sample magnetometer.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

The nonlinear evolution of a thin monoenergetic electron beam injected in a magnetized plasma and interacting with a whistler wave packet through Cherenkov resonance is considered. It is shown that effective dissipation due to whistlers' wave field leakage out of the bounded beam volume to infinity (effective radiation outside the beam) strongly influences the evolution of the beam electrons' distribution. Self-organization of beam structure leads to the formation of electron bunches continuously decelerated by waves. In the presence of effective energy losses, the phases of all waves in the packet can become strongly correlated and thus can prevent the stochastic phase mixing required for validity of quasilinear theory. In the asymptotic stage of the beam–waves interaction, dynamically stable electron bunches are present together with a diffusion plateau in the velocity distribution; these nonlinear structures allow the beam to radiate wave energy on a significative distance from its injection point. © 2000 American Institute of Physics.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

Whistler wave excitation in a magnetized laboratory plasma by a density modulated electron beam is studied for frequency modulation below, but in the range of, the electron gyrofrequency. When the beam velocity differs from the phase velocity of the whistler at the frequency modulation of the beam, a whistler wave, and, by Cerenkov emission, a beam wave at the same frequency are excited as single poles. When both velocities are equal, a resonance occurs leading to a maximum in the emission of whistler waves. The experiment performed in a magnetized plasma (np≈1011 cm−3, Te≈0.2 eV, B≈100 G) with a modulated electron beam (nb≈109 cm−3, Eb≈300 eV) is in agreement with a simple model which predicts the characteristics of the excited waves.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

Through Cerenkov emission, the interaction of an electron beam with a plasma leads to the excitation of whistler waves. Particle-in-cell simulations show that, when the beam is injected at an angle with respect to the magnetic field, the whistler wave emission of a modulated beam is increased compared to the same beam without modulation. This increased emission is related to the transfer of energy which occurs between the electrostatic mode directly excited by the density modulation and the electromagnetic whistler. This transfer of energy requires that the electrostatic field has a component perpendicular to the magnetic field. © 1994 American Institute of Physics.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

The theory of whistler wave interaction with a modulated electron beam injected obliquely to the magnetic field in an unbounded space plasma is considered. The study of the energy transfer between the spiraling beam and the whistler wave is done in the case of sheared whistlers, when the parallel wave number is very small compared to the perpendicular one. In the linear regime, structures of potentials and electromagnetic fields in the beam vicinity and in the wave zone are obtained analytically: Simple expressions for field components are provided for Cerenkov and Doppler resonances, in double and single pole cases. Emitted power is calculated as a function of beam parameters. © 1996 American Institute of Physics.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

The nonlinear theory of a thin modulated electron beam interaction with a monochromatic whistler wave is considered. The self-consistent set of differential equations describing the wave amplitude evolution and the beam particle motion has been solved by a computer code. Results issued from the numerical solution of the differential system are discussed, namely the physical features of the nonlinear beam–wave interaction (trapping, slowing down of the beam, wave damping, multiple bunching, beam focusing), as well as the influence of the physical parameters on the wave emission: beam energy and density, initial beam velocity distribution, and beam current modulation. It has been shown that the trapped particles are the source of the emission; they are decelerated in phase with the wave and remain in Cherenkov resonance with it owing to a nonlinear shift of the parallel wave number. No quasiperiodic exchange of energy between the wave and the particles has been observed. Time evolution of the wave amplitude and the particle energy has been explained by a simple model, as well as the multibunched structures appearing in the particle dynamics for certain physical parameters. © 1998 American Institute of Physics.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

The theory of whistler wave interaction with a modulated electron beam of finite radius and injected parallel to the magnetic field in an unbounded space plasma is considered. The study of the energy transfer between the thin beam and the whistler wave is done in the case of sheared whistlers, when the parallel wave number is very small compared to the perpendicular one. In this case, and in the linear regime, structures of potentials and electromagnetic fields inside and outside the beam are determined analytically. In the vicinity of the beam, simple expressions for field components are provided in the case of Cerenkov resonance near the double pole. © 1995 American Institute of Physics.

Electronic Resource

1471-4159

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

In recent studies of transgenic models of Alzheimer's disease (AD), it has been reported that antibodies to aged beta amyloid peptide 1–42 (Aβ1−42) solutions (mixtures of Aβ monomers, oligomers and amyloid fibrils) cause conspicuous reduction of amyloid plaques and neurological improvement. In some cases, however, neurological improvement has been independent of obvious plaque reduction, and it has been suggested that immunization might neutralize soluble, non-fibrillar forms of Aβ. It is now known that Aβ toxicity resides not only in fibrils, but also in soluble protofibrils and oligomers. The current study has investigated the immune response to low doses of Aβ1−42 oligomers and the characteristics of the antibodies they induce. Rabbits that were injected with Aβ1−42 solutions containing only monomers and oligomers produced antibodies that preferentially bound to assembled forms of Aβ in immunoblots and in physiological solutions. The antibodies have proven useful for assays that can detect inhibitors of oligomer formation, for immunofluorescence localization of cell-attached oligomers to receptor-like puncta, and for immunoblots that show the presence of SDS-stable oligomers in Alzheimer's brain tissue. The antibodies, moreover, were found to neutralize the toxicity of soluble oligomers in cell culture. Results support the hypothesis that immunizations of transgenic mice derive therapeutic benefit from the immuno-neutralization of soluble Aβ-derived toxins. Analogous immuno-neutralization of oligomers in humans may be a key in AD vaccines.

Electronic Resource

1471-4159

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract: The effect of the Kunitz proteinase inhibitor (KPI) on potential β-amyloid precursor protein (βPP)-processing activities from control and Alzheimer's disease (AD) brains was examined using fluorogenic substrates designed to mimic the secretory and amyloidogenic cleavages in βPP. In addition, the level of secretion of KPI-containing βPP751 and KPI-lacking βPP695 from transfected cells was examined to assess the effect of the KPI on βPP secretion. βPP751 and βPP695, obtained from conditioned media of transfected cells, had no effect on proteinase activities against the secretory and amyloidogenic substrates in extracts from control and AD brains. At similar concentrations βPP751, but not βPP695, completely inhibited the activity of trypsin against these substrates. Serine proteinase inhibitors had only modest effects on activities from brain, whereas cysteine modification completely inhibited them, indicating that these proteinase activities were not of the serine type. Thus, the results do not support a role for the KPI in the secretion of βPP or in the amyloidogenic cleavage of βPP. The amounts of βPP695 and βPP751 collected from the media of transfected cells after 48 h of growth were similar, indicating an equal rate of secretion. This result suggests that the KPI domain in βPP751 did not inhibit the secretory cleavage in transfected cells.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We report on a new passivation procedure of the GaAs surface based on a thermal treatment under a PH3 overpressure. This treatment results, by As/P exchange, in the formation of a thin superficial GaP layer which prevents the formation of an arsenic oxide, as observed by x-ray photoelectron spectroscopy analysis. Subsequent increase of the photoluminescence signal indicates improved electronic properties of GaAs surfaces as a result of this passivation procedure.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Electronic Resource

1077-3118

AIP Digital Archive

Physics

The discovery of current-switchable bi-stable remanent domain configurations on small ferromagnetic islands is reported. Rectangular NiFe islands with a thickness of 50 to 100 nm and lateral dimensions on the order of several microns were imaged using magnetic force microscopy after application of 10 ns current pulses through the material. The closure configuration can be set into either the 4 or 7 domain configuration by applying positive or negative current polarity at density on the order 107 A/cm2. The chirality of the closure patterns is fixed, implying that only two rather than four states are stable in these patterns. The possibility of using these configurations as a means of storing a logic state for memory applications is discussed. © 2002 American Institute of Physics.

Electronic Resource

1749-6632

Blackwell Publishing Journal Backfiles 1879-2005

Natural Sciences in General

Electronic Resource

1749-6632

Blackwell Publishing Journal Backfiles 1879-2005

Natural Sciences in General

Electronic Resource

1749-6632

Blackwell Publishing Journal Backfiles 1879-2005

Natural Sciences in General

Electronic Resource

1471-0528

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Objective  To investigate the effect of oral iron on postpartum red cell and iron parameters in non-anaemic women with iron deficiency.Design  Randomised study of supplementation with oral iron sulphate 80 mg daily or placebo for 12 weeks starting 24−48 hours after delivery, with visits antepartum and 1, 4, 6 and 12 weeks postpartum.Setting  Swiss university hospital obstetric unit.Participants  Fifty-two women with antenatal iron deficiency (serum ferritin 〈15 μg/L) and no antenatal or postnatal anaemia (haemoglobin 〉11 g/dL up to 48 hours before delivery, and 〉10 g/dL postpartum), divided into two groups comparable in antenatal iron status.Methods  Supplementation was started 24–48 hours after delivery (visit 1:V1). Additional tablets were issued one week after V1 (V2), four weeks after V1 (V3) and six weeks after V1 (V4). The last visit took place 12 weeks after visit 1 and 6 weeks after visit 4 (V5). Patients were required to return blisters and boxes whether they were used and unused at each visit and compliance was assessed by counting the tablets. Blood samples for haematology and iron status testing were taken before delivery and at each visit.Main outcome measures  Iron status (serum ferritin, hypochromic red cells, iron, transferrin saturation, soluble transferrin receptor concentration); erythropoiesis (standard parameters, including reticulocyte indices); and inflammatory response (serum neopterin, C-reactive protein, white cell count) in five-datapoint profiles.Results  Increased ferritin (P= 0.0004) and transferrin saturation (P= 0.03), decreased soluble transferrin receptors (P= 0.02); increased haemoglobin (P= 0.02) and decreased hypochromic red cells (P= 0.04) compared with placebo at 12 weeks, with no differences in other red cell or reticulocyte parameters. There was a positive correlation between C-reactive protein and postpartum ferritin. No correlation was observed in the puerperium between C-reactive protein and hypochromic red cells or soluble transferrin receptors.Conclusions  Haemoglobin levels and iron stores in women with term gestational iron deficiency benefit significantly from iron supplementation compared with placebo, even in an industrialised population.

Electronic Resource