6,160 research outputs found
Private Label Price Rigidity during Holiday Periods
Using weekly retail transaction scanner price data from a large U.S supermarket chain, we find significantly higher retail price rigidity for private label products than for nationally branded products during the Christmas and Thanksgiving holiday periods relative to the rest of the year. The finding cannot be explained by changes in holiday period promotional practices because we find that private label promotions appear to diminish at least as much as national brands. The increased rigidity of private label products relative to national brands is only partially accounted for by increased rigidity of wholesale prices. After ruling out other potential explanations, we suggest that the higher private label price rigidity might be due to the increased emphasis on social consumption during holiday periods, raising the customersâ value of nationally branded products relative to the private labels.Price Rigidity, Holidays, Private Label, National Brand, Social Consumption
Dark matter scenarios in a constrained model with Dirac gauginos
We perform the first analysis of Dark Matter scenarios in a constrained model
with Dirac Gauginos. The model under investigation is the Constrained Minimal
Dirac Gaugino Supersymmetric Standard model (CMDGSSM) where the Majorana mass
terms of gauginos vanish. However, -symmetry is broken in the Higgs sector
by an explicit and/or effective -term. This causes a mass splitting
between Dirac states in the fermion sector and the neutralinos, which provide
the dark matter candidate, become pseudo-Dirac states. We discuss two
scenarios: the universal case with all scalar masses unified at the GUT scale,
and the case with non-universal Higgs soft-terms. We identify different regions
in the parameter space which fullfil all constraints from the dark matter
abundance, the limits from SUSY and direct dark matter searches and the Higgs
mass. Most of these points can be tested with the next generation of direct
dark matter detection experiments.Comment: 28 pages, 11 figures; v2: minor changes, title modified; matches
published versio
Holiday Price Rigidity and Cost of Price Adjustment
The Thanksgiving-Christmas holiday period is a major sales period for US retailers. Due to higher store traffic, tasks such as restocking shelves, handling customersâ questions and inquiries, running cash registers, cleaning, and bagging, become more urgent during holidays. As a result, the holiday-period opportunity cost of price adjustment may increase dramatically for retail stores, which should lead to greater price rigidity during holidays. We test this prediction using weekly retail scanner price data from a major Midwestern supermarket chain. We find that indeed, prices are more rigid during holiday periods than non-holiday periods. For example, the econometric model we estimate suggests that the probability of a price change is lower during holiday periods, even after accounting for cost changes. Moreover, we find that the probability of a price change increases with the size of the cost change, during both, the holiday as well as non-holiday periods. We argue that these findings are best explained by higher price adjustment costs (menu cost) the retailers face during the holiday periods. Our data provides a natural experiment for studying variation in price rigidity because most aspects of market environment such as market structure, industry concentration, the nature of long-term relationships, contractual arrangements, etc., do not vary between holiday and nonholiday periods. We, therefore, are able to rule out these commonly used alternative explanations for the price rigidity, and conclude that the menu cost theory offers the best explanation for the holiday period price rigidity.
By-passing the Kohn-Sham equations with machine learning
Last year, at least 30,000 scientific papers used the Kohn-Sham scheme of
density functional theory to solve electronic structure problems in a wide
variety of scientific fields, ranging from materials science to biochemistry to
astrophysics. Machine learning holds the promise of learning the kinetic energy
functional via examples, by-passing the need to solve the Kohn-Sham equations.
This should yield substantial savings in computer time, allowing either larger
systems or longer time-scales to be tackled, but attempts to machine-learn this
functional have been limited by the need to find its derivative. The present
work overcomes this difficulty by directly learning the density-potential and
energy-density maps for test systems and various molecules. Both improved
accuracy and lower computational cost with this method are demonstrated by
reproducing DFT energies for a range of molecular geometries generated during
molecular dynamics simulations. Moreover, the methodology could be applied
directly to quantum chemical calculations, allowing construction of density
functionals of quantum-chemical accuracy
Monitoring surface charge movement in single elongated semiconductor nanocrystals
Journal ArticleWe demonstrate a universal correlation between the spectral linewidth and position of the excitonic transition in the spectral jitter observed from single elongated colloidal quantum dots. Breaking the symmetry of electron and hole confinement as well as of the spatial directions for surface charge diffusion enables us to microscopically track meandering surface charges, providing a novel probe of the particle's nanoenvironment. Spectral diffusion exhibits only a weak temperature dependence, which allows us to uncover the single particle homogeneous linewidth of 50 meVat room temperature
Air-induced fluorescence bursts from single semiconductor nanocrystals
Journal ArticleWe observe a dramatic enhancement of the fluorescence intensity from single core/shell CdSe/ZnS nanocrystals upon sudden exposure to air from an evacuated surrounding. Both the number of particles contributing to emission increases as well as the average emission intensity from a single particle, leading to an overall fluorescence rise by a factor of 60. A common power-law distribution of both on- and off times of single nanocrystals is observed independent of shell thickness and environment. We propose that electron transfer to oxygen, which is facilitated by the presence of water, leads to a neutralization of charged, nonemissive nanocrystals
Design and stratification of PASS : a new panel study for research on long term unemployment
"The paper introduces the general design features and particularities of a new largescale panel study for research on recipients of benefits for the long-term unemployed (the so called Unemployment Benefit II) in Germany that combines a sample of 6000 recipient households with an equally large sample of the general population. Particular focus is on the sampling procedure for the general population, where a commercial database was used to draw a sample stratified by status." (Author's abstract, IAB-Doku) ((en))IAB-Haushaltspanel - Konzeption, empirische Sozialforschung, Erhebungsmethode, Stichprobe, Langzeitarbeitslosigkeit
Virtual learning environment for interactive engagement with advanced quantum mechanics
A virtual learning environment can engage university students in the learning
process in ways that the traditional lectures and lab formats can not. We
present our virtual learning environment \emph{StudentResearcher} which
incorporates simulations, multiple-choice quizzes, video lectures and
gamification into a learning path for quantum mechanics at the advanced
university level. \emph{StudentResearcher} is built upon the experiences
gathered from workshops with the citizen science game Quantum Moves at the
high-school and university level, where the games were used extensively to
illustrate the basic concepts of quantum mechanics. The first test of this new
virtual learning environment was a 2014 course in advanced quantum mechanics at
Aarhus University with 47 enrolled students. We found increased learning for
the students who were more active on the platform independent of their previous
performances.Comment: 8 pages, 6 figure
Relative importance of fertiliser addition to plants and exclusion of predators for aphid growth in the field
Herbivore dynamics and community structure are influenced both by plant quality and the actions of natural enemies. A factorial experiment manipulating both higher and lower trophic levels was designed to explore the determinants of colony growth of the aphid Aphis jacobaeae, a specialist herbivore on ragwort Senecio jacobaea. Potential plant quality was manipulated by regular addition of NPK-fertiliser and predator pressure was reduced by interception traps; the experiment was carried out at two sites. The size and persistence of aphid colonies were measured. Fertiliser addition affected plant growth in only one site, but never had a measurable effect on aphid colony growth. In both habitats the action of insect predators dominated, imposing strong and negative effects on aphid colony performance. Ants were left unmanipulated in both sites and their performance on the aphid colonies did not significantly differ between sites or between treatments. Our results suggest that, at least for aphid herbivores on S. jacobaea, the action of generalist insect predators appears to be the dominant factor affecting colony performance and can under certain conditions even improve plant productivit
- âŠ