1,858 research outputs found
Modelling and evaluation of load and performance control mechanisms of B-ISDN/ATM switching systems
Behandelt wird die Problematik der Last- und Leistungsregelung im Kontext der ATM-basierten Breitband-Vermittlungstechnik.Objective of this thesis are load control and performance control concepts for broadband switching systems. Focus is the services integrating network technology B-ISDN using ATM as transfer mode. The studied mechanisms and concepts are principally of generic nature. Specifically they are designed within the envisaged context of B-ISDN, due to its extensive vision with respect to service integration, Quality of Service (QoS) support and ATM bearer capabilities.
Area of application is implicitly the network control plane, but interactions between user and control plane have to be considered, too. The prime scope are switching nodes between access and core network domain, i.e., B-ISDN switches which have to provide user-to-network and network-to-network signalling protocol functions. Thus, beside service distinction call type differentiation is also covered due to the considered network positioning
Detection of water absorption in the day side atmosphere of HD 189733 b using ground-based high-resolution spectroscopy at 3.2 microns
We report a 4.8 sigma detection of water absorption features in the day side
spectrum of the hot Jupiter HD 189733 b. We used high-resolution (R~100,000)
spectra taken at 3.2 microns with CRIRES on the VLT to trace the
radial-velocity shift of the water features in the planet's day side atmosphere
during 5 h of its 2.2 d orbit as it approached secondary eclipse. Despite
considerable telluric contamination in this wavelength regime, we detect the
signal within our uncertainties at the expected combination of systemic
velocity (Vsys=-3 +5-6 km/s) and planet orbital velocity (Kp=154 +14-10 km/s),
and determine a H2O line contrast ratio of (1.3+/-0.2)x10^-3 with respect to
the stellar continuum. We find no evidence of significant absorption or
emission from other carbon-bearing molecules, such as methane, although we do
note a marginal increase in the significance of our detection to 5.1 sigma with
the inclusion of carbon dioxide in our template spectrum. This result
demonstrates that ground-based, high-resolution spectroscopy is suited to
finding not just simple molecules like CO, but also to more complex molecules
like H2O even in highly telluric contaminated regions of the Earth's
transmission spectrum. It is a powerful tool that can be used for conducting an
immediate census of the carbon- and oxygen-bearing molecules in the atmospheres
of giant planets, and will potentially allow the formation and migration
history of these planets to be constrained by the measurement of their
atmospheric C/O ratios.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letter
Slinky Inflation
We present a new approach to quintessential inflation, in which both dark
energy and inflation are explained by the evolution of a single scalar field.
We start from a simple scalar potential with both oscillatory and exponential
behavior. We employ the conventional reheating mechanism of new inflation, in
which the scalar decays to light fermions with a decay width that is
proportional to the scalar mass. Because our scalar mass is proportional to the
Hubble rate, this gives adequate reheating at early times while shutting off at
late times to preserve quintessence and satisfy nucleosynthesis constraints.
We discuss a simple model which solves the horizon, flatness, and "why now"
problems. Without any additional tuning of parameters, this model satisfies all
constraints from CMB, large scale structure, and nucleosynthesis. The
predictions for the inflationary spectral indices are n_S = n_T = 1. In this
model we are currently beginning the third cosmic epoch of accelerated
expansion.Comment: 5 pages, 2 color figures, 1 tabl
Calabi-Yau Duals for CHL Strings
We find M-theory (Type IIA) duals for compactifications of the 9d CHL string
to 5d (4d) on K3 (K3 x S^1). The IIA duals are Calabi-Yau orbifolds with
nontrivial RR U(1) backgrounds turned on.Comment: 16 pages, harvma
DNA as a programmable viscoelastic nanoelement
The two strands of a DNA molecule with a repetitive sequence can pair into
many different basepairing patterns. For perfectly periodic sequences, early
bulk experiments of Poerschke indicate the existence of a sliding process,
permitting the rapid transition between different relative strand positions
[Biophys. Chem. 2 (1974) 83]. Here, we use a detailed theoretical model to
study the basepairing dynamics of periodic and nearly periodic DNA. As
suggested by Poerschke, DNA sliding is mediated by basepairing defects (bulge
loops), which can diffuse along the DNA. Moreover, a shear force f on opposite
ends of the two strands yields a characteristic dynamic response: An outward
average sliding velocity v~1/N is induced in a double strand of length N,
provided f is larger than a threshold f_c. Conversely, if the strands are
initially misaligned, they realign even against an external force less than
f_c. These dynamics effectively result in a viscoelastic behavior of DNA under
shear forces, with properties that are programmable through the choice of the
DNA sequence. We find that a small number of mutations in periodic sequences
does not prevent DNA sliding, but introduces a time delay in the dynamic
response. We clarify the mechanism for the time delay and describe it
quantitatively within a phenomenological model. Based on our findings, we
suggest new dynamical roles for DNA in artificial nanoscale devices. The
basepairing dynamics described here is also relevant for the extension of
repetitive sequences inside genomic DNA.Comment: 10 pages, 7 figures; final version to appear in Biophysical Journa
Cost evaluation of an innovative outreach clinic across social insurance codes in rural Northern Germany - A routine data analysis
A community outreach clinic was established in 2013 in a rural part of Germany to counsel and better integrate patients with mental health disorders or clients with psychosocial problems into the healthcare and complementary social assistance system. In a pilot study, we aimed to evaluate the costs of the integration assistance system after the outreach clinic was opened, the number of visits and the trend in the costs of the social assistance system of the federal state. Anonymised secondary cost data were used to evaluate the costs associated with the integration assistance receivers before (2010–2012) and after the establishment of the outreach clinic (2013–2015). Total costs were descriptively compared between the intervention group (consultation in the outreach clinic), the non-referral group, and a propensity score-matched control group for the years 2013–2015. To monitor the counselling activity, we used anonymised data on visits to the outreach clinic between 2013 and 2015. Data from 50 clients in the outreach clinic and 678 non-referral clients were analysed. The total costs of the integration assistance for the years 2013–2015 amounted to EUR 21,516 (95% CI 14,513–28,518) and EUR 28,464 (25,789–31,140) respectively. Propensity score matching of the controls resulted in equalised total costs for the years 2013 through 2015 for clients (n = 50, EUR 21,516 (14,513–28,518)) and controls (n = 250, EUR 21,725 (18,214–25,234)). The total number of integration assistance receivers in the district was lower than the average for the federal state. The number of consultations at the outpatient clinic steadily increased from 146 in 2013 to 1,090 in 2015. Counselling in the outreach clinic might help reduce the placement of clients into integration assistance, including supported housing, and slow the expected cost trend. However, counselling failed to lower total costs in the integration assistance service, possibly due to the selection of more severe cases
Monomolecular and Bimolecular Recombination of Electron-Hole Pairs at the Interface of a Bilayer Organic Solar Cell
While it has been argued that field-dependent geminate pair recombination (GR) is important, this process is often disregarded when analyzing the recombination kinetics in bulk heterojunction organic solar cells (OSCs). To differentiate between the contributions of GR and nongeminate recombination (NGR) the authors study bilayer OSCs using either a PCDTBTtype polymer layer with a thickness from 14 to 66 nm or a 60 nm thick p-DTS(FBTTh2)(2) layer as donor material and C-60 as acceptor. The authors measure JV-characteristics as a function of intensity and charge-extraction-by-linearly-increasing-voltage-type hole mobilities. The experiments have been complemented by Monte Carlo simulations. The authors find that fill factor (FF) decreases with increasing donor layer thickness (L-p) even at the lowest light intensities where geminate recombination dominates. The authors interpret this in terms of thickness dependent back diffusion of holes toward their siblings at the donor-acceptor interface that are already beyond the Langevin capture sphere rather than to charge accumulation at the donor-acceptor interface. This effect is absent in the p-DTS(FBTTh2)(2) diode in which the hole mobility is by two orders of magnitude higher. At higher light intensities, NGR occurs as evidenced by the evolution of s-shape of the JV-curves and the concomitant additional decrease of the FF with increasing layer thickness.The authors acknowledge financial support by the Bavarian State Ministry
of Science, Research, and the Arts through the Collaborative Research
Network “Solar Technologies go Hybrid”, by the Volkswagen foundation
and by the German Science Foundation DFG through the doctoral
training center “GRK 1640.” This project further received funding from
the Universidad Carlos III de Madrid, the European Union’s Seventh
Framework Programme for research, technological development and
demonstration under grant agreement no. 600371, el Ministerio de EconomĂa y Competitividad (COFUND2014-51509), el Ministerio de
EducaciĂłn, cultura y Deporte (CEI-15-17), and Banco Santander. M.R.
additionally acknowledges support from the Hanns Seidel Foundation
for a stipend through funds from the German Ministry of Education
and Research (BMBF). T.-Q.N. thanks the Office of Naval Research
(#N000141410076) for the support. Furthermore, the authors would like
to thank the anonymous referees for helpful suggestions
Nonequilibrium dynamics: a renormalized computation scheme
We present a regularized and renormalized version of the one-loop nonlinear
relaxation equations that determine the non-equilibrium time evolution of a
classical (constant) field coupled to its quantum fluctuations. We obtain a
computational method in which the evaluation of divergent fluctuation integrals
and the evaluation of the exact finite parts are cleanly separated so as to
allow for a wide freedom in the choice of regularization and renormalization
schemes. We use dimensional regularization here. Within the same formalism we
analyze also the regularization and renormalization of the energy-momentum
tensor. The energy density serves to monitor the reliability of our numerical
computation. The method is applied to the simple case of a scalar phi^4 theory;
the results are similar to the ones found previously by other groups.Comment: 15 pages, 9 postscript figures, revtex; version published in Phys.
Rev, with minor corrections; improves the first version of 1996 by including
the discussion of energy momentum tenso
Formation & evolution of cosmic superstrings: a short review
I will briefly review the formation and evolution of cosmic superstrings, in
the context of brane-world cosmological models within M-theory. These objects
can play the role of cosmic strings, offering a variety of astrophysical
consequences, which I will briefly discuss.Comment: 4 pages; invited talk in the workshop on Cosmology-Strings:
Theory-Cosmology-Phenomenology, Corfu (Greece), Sept. 200
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