532 research outputs found
Die Prädiktion von Schwangerschaftserkrankungen im 1. Trimenon mittels des biochemischen Parameters papp-a
Die vorliegende Arbeit prüft die Wertigkeit des biochemischen Screenings im 1.Trimenon mit dem maternalen Serumparameter papp-a im Hinblick auf folgende Schwangerschaftserkrankungen. Gegenstand dieser Studie sind 401 Schwangerschaften, bei denen im Rahmen der Fehlbildungdiagnostik im 1.Trimenon der SS eine Blutprobe zur Bestimmung des papp-a Wertes entnommen wurde. Den Schwangeren wurde ein Fragebogen zum Outcome der Schwangerschaft mitgegeben. Folgende Parameter waren für unsere Studie relevant: Präeklampsie, IUWR, Frühgeburtlichkeit, Blutung im 1. Trimenon, Nikotinkonsum während der SS und Erkrankungen in der Verwandtschaft. Es zeigte sich ein signifikant niedrigerer papp-a Wert bei später wachstumsretardiert geborenen Kindern. Erstmalig wird in dieser Studie beschreiben, dass bei Schwangeren mit einem papp-a (mom)-Wert > 2 mit einer mittleren bis hohen Wahrscheinlichkeit keine der oben genannten Schwangerschaftserkrankungen vorliegt
The Grover algorithm with large nuclear spins in semiconductors
We show a possible way to implement the Grover algorithm in large nuclear
spins 1/2<I<9/2 in semiconductors. The Grover sequence is performed by means of
multiphoton transitions that distribute the spin amplitude between the nuclear
spin states. They are distinguishable due to the quadrupolar splitting, which
makes the nuclear spin levels non-equidistant. We introduce a generalized
rotating frame for an effective Hamiltonian that governs the non-perturbative
time evolution of the nuclear spin states for arbitrary spin lengths I. The
larger the quadrupolar splitting, the better the agreement between our
approximative method using the generalized rotating frame and exact numerical
calculations.Comment: 11 pages, 18 EPS figures, REVTe
Tidal Dwarf Galaxies at Intermediate Redshifts
We present the first attempt at measuring the production rate of tidal dwarf
galaxies (TDGs) and estimating their contribution to the overall dwarf
population. Using HST/ACS deep imaging data from GOODS and GEMS surveys in
conjunction with photometric redshifts from COMBO-17 survey, we performed a
morphological analysis for a sample of merging/interacting galaxies in the
Extended Chandra Deep Field South and identified tidal dwarf candidates in the
rest-frame optical bands. We estimated a production rate about 1.4 {\times}
10^{-5} per Gyr per comoving volume for long-lived TDGs with stellar mass 3
{\times} 10^{8-9} solar mass at 0.5<z<1.1. Together with galaxy merger rates
and TDG survival rate from the literature, our results suggest that only a
marginal fraction (less than 10%) of dwarf galaxies in the local universe could
be tidally-originated. TDGs in our sample are on average bluer than their host
galaxies in the optical. Stellar population modelling of optical to
near-infrared spectral energy distributions (SEDs) for two TDGs favors a burst
component with age 400/200 Myr and stellar mass 40%/26% of the total,
indicating that a young stellar population newly formed in TDGs. This is
consistent with the episodic star formation histories found for nearby TDGs.Comment: 9 pages, 5 figures, Accepted for publication in Astrophysics & Space
Scienc
Spin-orbit effects on two-electron states in nanowhisker double quantum dots
We investigate theoretically the combined effects of the electron-electron
and the Rashba spin-orbit interactions on two electrons confined in
quasi-one-dimensional AlInSb-based double quantum dots. We calculate the
two-electron wave functions and explore the interplay between these two
interactions on the energy levels and the spin of the states. The energy
spectrum as a function of an applied magnetic field shows crossings and
anticrossings between triplet and singlet states, associated with level mixing
induced by the spin-orbit coupling. We find that the fields at which these
crossings occur can be naturally controlled by the interdot barrier width,
which controls the exchange integral in the structure.Comment: 5 pages, 6 figure
Coherent multiple light scattering in Faraday active materials
Wave propagation in multiple scattering media shows various kinds of coherent phenomena such as coherent backscattering [1, 2] or Anderson localization [3], both of which are intimately connected to the concept of reciprocity. Manipulating reciprocity in such media is a powerful tool to study these phenomena in experiments [4]. Here we discuss the manipulation of reciprocity in reflection and transmission geometry for the case of light propagation in magneto-optical media. We show new experiments on coherent backscattering and speckle correlations in strongly scattering samples containing Faraday active materials (CeF3) with transport mean free path in the μm range, at low temperatures (T < 10 K) and high fields (B = 18 T). Under such conditions we observe the effect of a Faraday rotation saturation in multiple scattering measurements.publishe
Non-linear response of a Kondo system: Perturbation approach to the time dependent Anderson impurity model
Nonlinear tunneling current through a quantum dot
(an Anderson impurity system) subject to both constant and alternating
electric fields is studied in the Kondo regime. A systematic diagram technique
is developed for perturbation study of the current in physical systems out of
equilibrium governed by time - dependent Hamiltonians of the Anderson and the
Kondo models. The ensuing calculations prove to be too complicated for the
Anderson model, and hence, a mapping on an effective Kondo problem is called
for. This is achieved by constructing a time - dependent version of the
Schrieffer - Wolff transformation. Perturbation expansion of the current is
then carried out up to third order in the Kondo coupling J yielding a set of
remarkably simple analytical expressions for the current. The zero - bias
anomaly of the direct current differential conductance is shown to be
suppressed by the alternating field while side peaks develop at finite source -
drain voltage. Both the direct component and the first harmonics of the time -
dependent response are equally enhanced due to the Kondo effect, while
amplitudes of higher harmonics are shown to be relatively small. A zero
alternating bias anomaly is found in the alternating current differential
conductance, that is, it peaks around zero alternating bias. This peak is
suppressed by the constant bias. No side peaks show up in the differential
alternating - conductance but their counterpart is found in the derivative of
the alternating current with respect to the direct bias. The results pertaining
to nonlinear response are shown to be valid also below the Kondo temperature.Comment: 55 latex pages 11 ps figure
Velocity-force characteristics of an interface driven through a periodic potential
We study the creep dynamics of a two-dimensional interface driven through a
periodic potential using dynamical renormalization group methods. We find that
the nature of weak-drive transport depends qualitatively on whether the
temperature is above or below the equilibrium roughening transition
temperature . Above , the velocity-force characteristics is Ohmic,
with linear mobility exhibiting a jump discontinuity across the transition. For
, the transport is highly nonlinear, exhibiting an interesting
crossover in temperature and weak external force . For intermediate drive,
, we find near a power-law velocity-force characteristics
, with , and well-below ,
, with . In the limit
of vanishing drive () the velocity-force characteristics crosses over
to , and is controlled by soliton nucleation.Comment: 18 pages, submitted to Phys. Rev.
Robust Magnetic Order Upon Ultrafast Excitation of an Antiferromagnet
The ultrafast manipulation of magnetic order due to optical excitation is governed by the intricate flow of energy and momentum between the electron, lattice, and spin subsystems. While various models are commonly employed to describe these dynamics, a prominent example being the microscopic three temperature model M3TM , systematic, quantitative comparisons to both the dynamics of energy flow and magnetic order are scarce. Here, an M3TM was applied to the ultrafast magnetic order dynamics of the layered antiferromagnet GdRh2Si2. The femtosecond dynamics of electronic temperature, surface ferromagnetic order, and bulk antiferromagnetic order were explored at various pump fluences employing time and angle resolved photoemission spectroscopy and time resolved resonant magnetic soft X ray diffraction, respectively. After optical excitation, both the surface ferromagnetic order and the bulk antiferromagnetic order dynamics exhibit two step demagnetization behaviors with two similar timescales lt;1 ps, amp; 8764;10 ps , indicating a strong exchange coupling between localized 4f and itinerant conduction electrons. Despite a good qualitative agreement, the M3TM predicts larger demagnetization than the experimental observation, which can be phenomenologically described by a transient, fluence dependent increased N el temperature. The results indicate that effects beyond a mean field description have to be considered for a quantitative description of ultrafast magnetic order dynamic
New fossil remains of Homo naledi from the Lesedi Chamber, South Africa
The Rising Star cave system has produced abundant fossil hominin remains within the
Dinaledi Chamber, representing a minimum of 15 individuals attributed to Homo naledi. Further
exploration led to the discovery of hominin material, now comprising 131 hominin specimens,
within a second chamber, the Lesedi Chamber. The Lesedi Chamber is far separated from the
Dinaledi Chamber within the Rising Star cave system, and represents a second depositional context
for hominin remains. In each of three collection areas within the Lesedi Chamber, diagnostic
skeletal material allows a clear attribution to H. naledi. Both adult and immature material is present.
The hominin remains represent at least three individuals based upon duplication of elements, but
more individuals are likely present based upon the spatial context. The most significant specimen is
the near-complete cranium of a large individual, designated LES1, with an endocranial volume of
approximately 610 ml and associated postcranial remains. The Lesedi Chamber skeletal sample
extends our knowledge of the morphology and variation of H. naledi, and evidence of H. naledi
from both recovery localities shows a consistent pattern of differentiation from other hominin
species.SP201
Scaling up local energy infrastructure; An agent-based model of the emergence of district heating networks
The potential contribution of local energy infrastructure – such as heat networks – to the transition to a low carbon economy is increasingly recognised in international, national and municipal policy. Creating the policy environment to foster the scaling up of local energy infrastructure is, however, still challenging; despite national policy action and local authority interest the growth of heat networks in UK cities remains slow. Technoeconomic energy system models commonly used to inform policy are not designed to address institutional and governance barriers. We present an agent-based model of heat network development in UK cities in which policy interventions aimed at the institutional and governance barriers faced by diverse actors can be explored. Three types of project instigators are included – municipal, commercial and community – which have distinct decision heuristics and capabilities and follow a multi-stage development process. Scenarios of policy interventions developed in a companion modelling approach indicate that the effect of interventions differs between actors depending on their capabilities. Successful interventions account for the specific motivations and capabilities of different actors, provide a portfolio of support along the development process and recognise the important strategic role of local authorities in supporting low carbon energy infrastructure
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