284 research outputs found
Coexistence of service- and facility-based competition: The relevance of access prices for "make-or-buy"-decisions
This paper models competition between two firms, which provide broadband Internet access in regional markets with different population densities. The firms, an incumbent and an entrant, differ in two ways. First, consumers bear costs when switching to the entrant. Second, the entrant faces a make-or-buy decision in each region and can choose between service-based and facility-based entry. The usual trade-off between static and dynamic efficiency does not apply in the sense that higher access fees might yield both, lower retail prices and higher total coverage. This holds despite a strategic effect in the entrant's investment decision. While investment lowers marginal costs in regions with facility-based entry, it intensifies competition in all regions. We show that the cost-reducing potential of investments dominates the strategic effect: Higher access fees increase facility-based competition, decrease retail prices and increase total demand. --Broadband access markets,facility- and service-based entry,investments,economies of density,switching costs
Coexistence of Service- and Facility-Based Competition: The Relevance of Access Prices for "Make-or-Buy"-Decisions
This paper models competition between two firms, which provide broadband Internet access in regional markets with different population densities. The firms, an incumbent and an entrant, differ in two ways. First, consumers bear costs when switching to the entrant. Second, the entrant faces a make-or-buy decision in each region and can choose between service-based and facility-based entry. The usual trade-off between static and dynamic eficiency does not apply in the sense that higher access fees might yield both, lower retail prices and higher total coverage. This holds despite a strategic effect in the entrant's investment decision. While investment lowers marginal costs in regions with facility-based entry, it intensifies competition in all regions. We show that the cost-reducing potential of investments dominates the strategic effect: Higher access fees increase facility-based competition, decrease retail prices and increase total demand.Broadband access markets, facility- and service-based entry, investments, economies of density, switching costs
The connection between star formation and stellar mass: Specific star formation rates to redshift one
We investigate the contribution of star formation to the growth of stellar
mass in galaxies over the redshift range 0.5 < z < 1.1 by studying the redshift
evolution of the specific star formation rate (SSFR), defined as the star
formation rate per unit stellar mass. We use an I-band selected sample of 6180
field galaxies from the Munich Near-Infrared Cluster Survey (MUNICS) with
spectroscopically calibrated photometric redshifts. The SSFR decreases with
stellar mass at all redshifts. The low SSFRs of massive galaxies indicates that
star formation does not significantly change their stellar mass over this
redshift range: The majority of massive galaxies have assembled the bulk of
their mass before redshift unity. Furthermore, these highest mass galaxies
contain the oldest stellar populations at all redshifts. The line of maximum
SSFR runs parallel to lines of constant star formation rate. With increasing
redshift, the maximum SFR is generally increasing for all stellar masses, from
SFR ~ 5 M_sun/yr at z = 0.5 to SFR ~ 10 M_sun/yr at z = 1.1. We also show that
the large SSFRs of low-mass galaxies cannot be sustained over extended periods
of time. Finally, our results do not require a substantial contribution of
merging to the growth of stellar mass in massive galaxies over the redshift
range probed. We note that highly obscured galaxies which remain undetected in
our sample do not affect these findings for the bulk of the field galaxy
population.Comment: 5 pages, 3 colour figures, accepted for publication in MNRAS Letter
Schr\"odinger operators with complex potential but real spectrum
Several aspects of complex-valued potentials generating a real and positive
spectrum are discussed. In particular, we construct complex-valued potentials
whose corresponding Schr\"odinger eigenvalue problem can be solved
analytically.Comment: 10, pages, LaTeX 2.09, 6 Postscript figures, uses amsfont, figures
available at http://faupt100.physik.uni-erlangen.de/junker/papers95-99.ht
Untersuchung zur elektronischen Tierkennzeichnung bei Ziegen
Bedingt durch die Einführung der elektronischen Tierkennzeichnung wurde eine Untersuchung mit vier verschiedenen Ohrmarken (Caisley, Hauptner Herberholz, Babyohrmarke von Hauptner Herberholz, Schlaufenohrmarke Shearwell) von Ende Januar bis November 2010 mit 115 Ziegenlämmern durchgeführt. Die o.g. Ohrmarken wurden zeitnah nach der Geburt eingezogen. In einer Variante wurden auch Ohrmarken (Caisley und Hauptner Herberholz) im Alter von neun Monaten appliziert
Erprobung eines Systems zur automatischen Verhaltenerfassung von Ziegenlämmern bei der „Beweidung“ von Futtergehölzen
To assess animal behaviour of goat kids on pasture, a real time positioning system, Ubisense 7000, was installed mobile and outdoors. One major goal of the study was to analyse time goat kids spent in functional areas like pasture, fodder hedges or hutch, the other goal was the feasibility of the positioning system regarding positioning of goats on pasture. Results show, that grazing periods happen even during the night, whereas fodder hedges were used only during daytime. Accuracy of the positioning concerning Euclidian geometry was around 15 cm, which is according manufacturer’s data
Untersuchung zur Verträglichkeit der elektronischen Tierkennzeichnung bei Ziegenlämmern ab der Geburt
Die dargestellte Studie ist ein Teilprojekt, in dem im Rahmen der elektronischen Tierkennzeichnung bei Ziegenlämmern zeitnah nach der Geburt vier verschiedene Ohrmarkentypen und deren Abheilung nach der Applikation sowie deren Verlustraten über einen Zeitraum von acht Wochen untersucht wurden.
Die elektronischen und visuellen Ohrmarken sind für den Einsatz bei Ziegenlämmern sehr gut geeignet. Es sind nur wenigen und leichte Entzündungen aufgetreten
Standardized Loads Acting in Hip Implants
With the increasing success of hip joint replacements, the average age of
patients has decreased, patients have become more active and their
expectations of the implant durability have risen. Thus, pre-clinical
endurance tests on hip implants require defining realistic in vivo loads from
younger and more active patients. These loads require simplifications to be
applicable for simulator tests and numerical analyses. Here, the contact
forces in the joint were measured with instrumented hip implants in ten
subjects during nine of the most physically demanding and frequent activities
of daily living. Typical levels and directions of average and high joint loads
were extracted from the intra- and inter-individually widely varying
individual data. These data can also be used to analyse bone remodelling at
the implant-bone interface, evaluate tissue straining in finite element
studies or validate analytical loading predictions, among other uses. The
current ISO standards for endurance tests of implant stems and necks are based
on historic analytical data from the 1970s. Comparisons of these test forces
with in vivo loads unveiled that their unidirectional orientations deviate
from the time-dependent in vivo directions during walking and most other
activities. The ISO force for testing the stem is substantially too low while
the ISO force for the neck better matches typical in vivo magnitudes. Because
the magnitudes and orientations of peak forces substantially vary among the
activities, load scenarios that reflect a collection of time-dependent high
forces should be applied rather than using unidirectional forces. Based on
data from ten patients, proposals for the most demanding activities, the time
courses of the contact forces and the required cycle numbers for testing are
given here. Friction moments in the joint were measured in addition to the
contact forces. The moment data were also standardized and can be applied to
wear tests of the implant. It was shown that friction only very slightly
influences the stresses in the implant neck and shaft
Specific star formation rates to redshift 5 from the FORS Deep Field and the GOODS-S Field
We explore the build-up of stellar mass in galaxies over a wide redshift
range 0.4 < z < 5.0 by studying the evolution of the specific star formation
rate (SSFR), defined as the star formation rate per unit stellar mass, as a
function of stellar mass and age. Our work is based on a combined sample of ~
9000 galaxies from the FORS Deep Field and the GOODS-S field, providing high
statistical accuracy and relative insensitivity against cosmic variance. As at
lower redshifts, we find that lower-mass galaxies show higher SSFRs than higher
mass galaxies, although highly obscured galaxies remain undetected in our
sample. Furthermore, the highest mass galaxies contain the oldest stellar
populations at all redshifts, in principle agreement with the existence of
evolved, massive galaxies at 1 < z < 3. It is remarkable, however, that this
trend continues to very high redshifts of z ~ 4. We also show that with
increasing redshift the SSFR for massive galaxies increases by a factor of ~
10, reaching the era of their formation at z ~ 2 and beyond. These findings can
be interpreted as evidence for an early epoch of star formation in the most
massive galaxies, and ongoing star-formation activity in lower mass galaxies.Comment: Accepted for publication in ApJL; 4 pages, 2 color figures, uses
emulateapj.cl
The Munich Near-Infrared Cluster Survey (MUNICS) - IX. Galaxy Evolution to z ~ 2 From Optically Selected Catalogues
(Abridged) We present B, R, and I-band selected galaxy catalogues based on
the Munich Near-Infrared Cluster Survey (MUNICS) which, together with the
K-selected sample, serve as an important probe of galaxy evolution in the
redshift range 0 < z < 2. Furthermore, used in comparison they are ideally
suited to study selection effects. The construction of the B, R, and I-selected
photometric catalogues, containing ~9000, ~9000, and ~6000 galaxies,
respectively, is described in detail. The catalogues reach 50% completeness
limits for point sources of B ~ 24.5mag, R ~ 23.5mag, and I ~ 22.5mag and cover
an area of about 0.3 square degrees. Photometric redshifts are derived for all
galaxies with an accuracy of dz/(1+z) ~ 0.057. We investigate the influence of
selection band and environment on the specific star formation rate (SSFR). We
find that K-band selection indeed comes close to selection in stellar mass,
while B-band selection purely selects galaxies in star formation rate. We use a
galaxy group catalogue constructed on the K-band selected MUNICS sample to
study possible differences of the SSFR between the field and the group
environment, finding a marginally lower average SSFR in groups as compared to
the field, especially at lower redshifts. The field-galaxy luminosity function
in the B and R band as derived from the R-selected sample evolves out to z ~ 2
in the sense that the characteristic luminosity increases but the number
density decreases. This effect is smaller at longer rest-frame wavelengths and
gets more pronounced at shorter wavelengths. Parametrising the redshift
evolution of the Schechter parameters as M*(z) = M*(0) + a ln(1+z) and Phi*(z)
= Phi*(0) (1+z)^b we find evolutionary parameters a ~ -2.1 and b ~ -2.5 for the
B band, and a ~ -1.4 and b ~ -1.8 for the R band.Comment: 23 pages, 19 figures; accepted for publication in MNRAS; version with
high-resolution figures will be made available at
http://www.usm.uni-muenchen.de/people/feulner/munics9/preprint_munics9.pd
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