232 research outputs found
Heavy Medal - The Consequences of Introducing Symbolic Awards on Contribution Behavior in Online Communities
Online communities, like Wikipedia and Stack Overflow, have made a vast repository of knowledge available as a public good. However, they suffer from under-contribution in terms of quantity and quality. To tackle this issue, online communities have increasingly been relying on gamification, the use of game elements in non-game settings, to incentivize their members. The consequences of introducing such features on members’ behavior have remained elusive—partly due to the lack of controlled experiments. Herein, we take advantage of a natural experiment in which a technical online community introduced gamified rewards, which are awarded contingent on performance thresholds—termed performance contingent symbolic awards. Employing a difference-in-differences design using a comparable online community as a control group, we find that the introduction of performance contingent symbolic awards has a negative impact on the contribution behavior overall and that experienced members reduce their contribution quantity while inexperienced members reduce their contribution quality
Higgs mass predictions of public NMSSM spectrum generators
The publicly available spectrum generators for the NMSSM often lead to
different predictions for the mass of the standard model-like Higgs boson even
if using the same renormalization scheme and two-loop accuracy. Depending on
the parameter point, the differences can exceed 5 GeV, and even reach 8 GeV for
moderate superparticle masses of up to 2 TeV. It is shown here that these
differences can be traced back to the calculation of the running standard model
parameters entering all calculations, to the approximations used in the
two-loop corrections included in the different codes, and to different choices
for the renormalization conditions and scales. In particular, the importance of
the calculation of the top Yukawa coupling is pointed out.Comment: 24 pages, no figures; v2: slightly extended discussion, matches
version accepted for publication by CP
Die Musikbibliothek von Carl Ferdinand Becker: Handschriften und Drucke der Becker-Bibliothek in einer Kabinettausstellung der Universitätsbibliothek Leipzig
Die Ausstellung veranschaulicht vom 24. Januar bis 14. April 2013 mittels einiger ausgewählter Handschriften und Drucke die Entstehung und Bedeutung der Bibliothek Carl Ferdinand Beckers. Es werden erste Stücke der Sammlung, seltene Drucke, unikale Quellen und Objekte gezeigt, die aufgrund ihrer Provenienz kulturgeschichtlich und musikhistorisch wertvolle Informationen enthalten. Oft besprochen, aber selten zu bewundern, überragt dabei das „Andreas- Bach-Buch“, eine Sammelhandschrift mit größtenteils einmaligen Klavier- und Orgelkompositionen des 17. und 18. Jahrhunderts aus dem Umfeld und partiell von der Hand Johann Sebastian Bachs die anderen Exponate
Precision tools and models to narrow in on the 750 GeV diphoton resonance
The hints for a new resonance at 750 GeV from ATLAS and CMS have triggered a
significant amount of attention. Since the simplest extensions of the standard
model cannot accommodate the observation, many alternatives have been
considered to explain the excess. Here we focus on several proposed
renormalisable weakly-coupled models and revisit results given in the
literature. We point out that physically important subtleties are often missed
or neglected. To facilitate the study of the excess we have created a
collection of 40 model files, selected from recent literature, for the
Mathematica package SARAH. With SARAH one can generate files to perform
numerical studies using the tailor-made spectrum generators FlexibleSUSY and
SPheno. These have been extended to automatically include crucial higher order
corrections to the diphoton and digluon decay rates for both CP-even and CP-odd
scalars. Additionally, we have extended the UFO and CalcHep interfaces of
SARAH, to pass the precise information about the effective vertices from the
spectrum generator to a Monte-Carlo tool. Finally, as an example to demonstrate
the power of the entire setup, we present a new supersymmetric model that
accommodates the diphoton excess, explicitly demonstrating how a large width
can be obtained. We explicitly show several steps in detail to elucidate the
use of these public tools in the precision study of this model.Comment: 184 pages, 24 figures; model files available at
http://sarah.hepforge.org/Diphoton_Models.tar.gz; v2: added a few
clarifications and reference
Reproduction, Embryonic Development, and Maternal Transfer of Contaminants in the Amphibian Gastrophryne carolinensis
Although many amphibian populations around the world are declining at alarming rates, the cause of most declines remains unknown. Environmental contamination is one of several factors implicated in declines and may have particularly important effects on sensitive developmental stages. Despite the severe effects of maternal transfer of contaminants on early development in other vertebrate lineages, no studies have examined the effects of maternal transfer of contaminants on reproduction or development in amphibians. We examined maternal transfer of contaminants in eastern narrow-mouth toads (Gastrophryne carolinensis) collected from a reference site and near a coal-burning power plant. Adult toads inhabiting the industrial area transferred significant quantities of selenium and strontium to their eggs, but Se concentrations were most notable (up to 100 μg/g dry mass). Compared with the reference site, hatching success was reduced by 11% in clutches from the contaminated site. In surviving larvae, the frequency of developmental abnormalities and abnormal swimming was 55–58% higher in the contaminated site relative to the reference site. Craniofacial abnormalities were nearly an order of magnitude more prevalent in hatchlings from the contaminated site. When all developmental criteria were considered collectively, offspring from the contaminated site experienced 19% lower viability. Although there was no statistical relationship between the concentration of Se or Sr transferred to eggs and any measure of offspring viability, our study demonstrates that maternal transfer may be an important route of contaminant exposure in amphibians that has been overlooked
Short-termed changes in quantitative ultrasound estimated bone density among young men in an 18-weeks follow-up during their basic training for the Swiss Armed Forces
Background
Quantitative Ultrasound (QUS) methods have been widely used to assess estimated bone density. This study aimed to assess changes in estimated bone density in association with changes in body composition, physical activity, and anthropometry.
Methods
We examined changes in anthropometry, body composition, and physical activity associated with changes in estimated bone mineral density (measured using quantitative ultrasound with a heel ultrasound device indicating broadband ultrasound attenuation BUA and speed of sound SOS) in a follow-up sample of n = 73 young men at the beginning and again 18 weeks later at the end of basic military training.
Results
At the end of the basic training, the subjects were on average significantly heavier (+1.0%), slightly taller (+0.5%) and had a higher fat mass (+6.6%) and grip strength (+8.6%). A significant decrease in mean physical activity (−49.5%) and mean estimated bone density calculated with BUA (−7.5%) was observed in the paired t-test. The results of the multivariable linear regressions (backward selection) show that changes in skeletal muscle mass (delta = 2nd measurement minus 1st measurement) have negative and body weight (delta) have positive association with the speed of sound SOS (delta), while fat mass (delta) and physical activity (delta) had the strongest negative associations with estimated bone mineral density (delta). In particular, we found a negative association between fat mass (delta) and estimated bone mineral density (delta, estimated with BUA).
Conclusion
Our study suggests that estimated bone density from the calcaneus can change within a few months even in young and mostly healthy individuals, depending upon physical activity levels and other co-factors. Further studies including other troop types as control groups as well as on women should follow in order to investigate this public health relevant topic in more depth. To what extent the estimated bone density measurement with quantitative ultrasound is clinically relevant needs to be investigated in further studies
Virtual signatures of dark sectors in Higgs couplings
Where collider searches for resonant invisible particles loose steam, dark
sectors might leave their trace as virtual effects in precision observables.
Here we explore this option in the framework of Higgs portal models, where a
sector of dark fermions interacts with the standard model through a strong
renormalizable coupling to the Higgs boson. We show that precise measurements
of Higgs-gauge and triple Higgs interactions can probe dark fermions up to the
TeV scale through virtual corrections. Observation prospects at the LHC and
future lepton colliders are discussed for the so-called singlet-doublet model
of Majorana fermions, a generalization of the bino-higgsino scenario in
supersymmetry. We advocate a two-fold search strategy for dark sectors through
direct and indirect observables.Comment: 20 pages, 7 figures, 1 tabl
Transient non-collinear magnetic state for all-optical magnetization switching
Resonant absorption of a photon by bound electrons in a solid can promote an
electron to another orbital state or transfer it to a neighboring atomic site.
Such a transition in a magnetically ordered material could affect the magnetic
order. While this process is an obvious road map for optical control of
magnetization, experimental demonstration of such a process remains
challenging. Exciting a significant fraction of magnetic ions requires a very
intense incoming light beam, as orbital resonances are often weak compared to
above-band-gap excitations. In the latter case, a sizeable reduction of the
magnetization occurs as the absorbed energy increases the spin temperature,
masking the non-thermal optical effects. Here, using ultrafast x-ray
spectroscopy, we were able to resolve changes in the magnetization state
induced by resonant absorption of infrared photons in Co-doped yttrium iron
garnet, with negligible thermal effects. We found that the optical excitation
of the Co ions affects the two distinct magnetic Fe sublattices differently,
resulting in a transient non-collinear magnetic state. The present results
indicate that the all-optical magnetization switching most likely occurs due to
the creation of a transient, non-collinear magnetic state followed by coherent
spin rotations of the Fe moments
Orbital dynamics during an ultrafast insulator to metal transition
Phase transitions driven by ultrashort laser pulses have attracted interest
both for understanding the fundamental physics of phase transitions and for
potential new data storage or device applications. In many cases these
transitions involve transient states that are different from those seen in
equilibrium. To understand the microscopic properties of these states, it is
useful to develop elementally selective probing techniques that operate in the
time domain. Here we show fs-time-resolved measurements of V Ledge Resonant
Inelastic X-Ray Scattering (RIXS) from the insulating phase of the Mott-
Hubbard material V2O3 after ultrafast laser excitation. The probed orbital
excitations within the d-shell of the V ion show a sub-ps time response, which
evolve at later times to a state that appears electronically indistinguishable
from the high-temperature metallic state. Our results demonstrate the potential
for RIXS spectroscopy to study the ultrafast orbital dynamics in strongly
correlated materials.Comment: 12 pages, 4 figure
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