Determination of oscillator strength of confined excitons in a semiconductor microcavity

We have achieved a significant experimental Rabi-splitting (3.4 meV) for confined polaritons in a planar semiconductor $\lambda$ microcavity for only a single quantum well (SQW) of GaAs (10 nm) placed at the antinode. The Rabi-splitting phenomena are discussed in detail based on the semiclassical theory, where two coupled harmonic oscillators (excitons and photons) are used to describe the system. In this way, we can obtain the dispersion curve of polaritons, the minimum value for the cavity reflectance and the oscillator strength to reach the strong coupling regime. This approach describes an ensemble of excitons confined in a SQW and includes a dissipation component. The results present a weak coupling regime, where an enhanced spontaneous emission takes place, and a strong coupling regime, where Rabi-splitting in the dispersion curve can be observed. The theoretical results are confronted with experimental data for the reflectance behavior in resonant and off-resonant conditions and present a great accuracy. This allows us to determine the oscillator strength of the confined excitons in the SQW with great precision.Comment: 11 pages, 7 figure

Lattice Gauge Fixing for Parameter Dependent Covariant Gauges

We propose a non-perturbative procedure to fix generic covariant gauges on the lattice. Varying the gauge parameter, this gauge fixing provides a concrete method to check numerically the gauge dependence of correlators measured on the lattice. The new algorithm turns out to converge with a good efficiency. As a preliminary physical result, we find a sensitive dependence of the gluon propagator on the gauge parameter.Comment: 10 pages (LaTeX2e), 5 eps figure

Optimal Path to Epigenetic Switching

We use large deviation methods to calculate rates of noise-induced transitions between states in multistable genetic networks. We analyze a synthetic biochemical circuit, the toggle switch, and compare the results to those obtained from a numerical solution of the master equation.Comment: 5 pages. 2 figures, uses revtex 4. PR-E reviewed for publicatio

Struktur Komunitas Moluska: Gastropoda dan Bivalvia di Vegetasi Perairan Danau Sentani Papua

Community structure of bivalvia and gastropods nearby water vegetation in Sentani Lake, Papua. Line’s transect and plot methods were used to determining the structure of mollusks and vegetation by using index, diversity, and dominance as parameters. Intentional measurement were carried out on several biological parameters of the waters at 10 sampling points. From the observation and measurments, we obtained seven types of mollusk with 5644 individuals, where six types are belong to gastropods and one type is a member of bivalves. The highest level of mollusk diversity was in Kwadeware, the highest at the inlet of the lake, and were dominated by Melanoides tuberculata and Pomacea canaliculata. In addition, vegetation found in the area observation were water hyacinth (Eichhornia crassipes), water spinach (Ipomoea aquatica), apu wood (Pistia stratiotes), genjer (Limnocharis flava), Hydrilla verticillata, seagrass (Potomogeton malainus), Nymphaea alba, Ceratophyllum demersum, and Nymphoides indica.Key words: gastropods; molluscs; vegetation; Sentani lak

Application of Precision Agriculture for the Sustainable Management of Fertilization in Olive Groves

Olive tree growing (Olea europaea L.) has considerably increased in the last decades, as has the consumption of extra virgin olive oil in the world. Precision agriculture is increasingly being applied in olive orchards as a new method to manage agronomic variability with the aim of providing individual plants with the right input amount, limiting waste or excess. The objective of this study was to develop a methodology on a GIS platform using GEOBIA algorithms in order to build prescription maps for variable rate (VRT) nitrogen fertilizers application in an olive orchard. The fertilization plan was determined for each tree by applying its own nitrogen balance, taking into account the variability of nitrogen in soil, leaf, production, and actual biometric and spectral conditions. Each olive tree was georeferenced using the S7-G Stonex instrument with real-time kinematic RTK positioning correction and the trunk cross section area (TCSA) was measured. Soil and leaves were sampled to study nutrient variability. Soil and plant samples were analyzed for all major physical and chemical properties. Spectral data were obtained using a multispectral camera (DJI multispectral) carried by an unmanned aerial vehicle (UAV) platform (DJI Phantom4). The biometric characteristics of the plants were extracted from the achieved normalized vegetation index (NDVI) map. The obtained prescription map can be used for variable rate fertilization with a tractor and fertilizer spreader connected via the ISOBUS system. Using the proposed methodology, the variable rate application of nitrogen fertilizer resulted in a 31% reduction in the amount to be applied in the olive orchard compared to the standard dose

Crowdfunding performance, market performance, and the moderating roles of product innovativeness and experts' judgment: Evidence from the movie industry

Reward-based crowdfunding (CF) has emerged as a method to solicit funds for innovative projects. Yet, little is still known about the ability of reward-based CF to act as a signal in the eyes of future consumers, and thus boost the future market performance of new products that innovators intend to commercialize using the campaign funds. In addition, scant research has clarified the boundary conditions that can magnify or weaken the efficacy of this CF signal. Given the relevance of reward-based CF for supporting innovation, understanding when the CF campaign performance works as an effective signal is of great interest, especially in business settings characterized by high product quality uncertainty. By using the movie industry as a setting, we contribute to fill this gap. Specifically, we argue that the positive effect of the reward-based CF performance is moderated by two important factors influencing consumers' purchase decisions: the degree of product innovativeness and the expert judgment about the product. Elaborating on the effects of product innovativeness, we posit that this product feature should moderate the positive relationship between CF and subsequent market performances in an inverted U-shaped fashion. Favorable expert recommendations, on the other hand, should weaken the efficacy of the CF performance as a signal. Results from a sample of 1059 new movies (of which 152 released in theaters) confirm these predictions and offer several remarkable implications for innovators

Determining the optimal piecewise constant approximation for the nonhomogeneous Poisson process rate of Emergency Department patient arrivals

Modeling the arrival process to an Emergency Department (ED) is the first step of all studies dealing with the patient flow within the ED. Many of them focus on the increasing phenomenon of ED overcrowding, which is afflicting hospitals all over the world. Since Discrete Event Simulation models are often adopted to assess solutions for reducing the impact of this problem, proper nonstationary processes are taken into account to reproduce time–dependent arrivals. Accordingly, an accurate estimation of the unknown arrival rate is required to guarantee the reliability of results. In this work, an integer nonlinear black–box optimization problem is solved to determine the best piecewise constant approximation of the time-varying arrival rate function, by finding the optimal partition of the 24 h into a suitable number of not equally spaced intervals. The black-box constraints of the optimization problem make the feasible solutions satisfy proper statistical hypotheses; these ensure the validity of the nonhomogeneous Poisson assumption about the arrival process, commonly adopted in the literature, and prevent mixing overdispersed data for model estimation. The cost function of the optimization problem includes a fit error term for the solution accuracy and a penalty term to select an adequate degree of regularity of the optimal solution. To show the effectiveness of this methodology, real data from one of the largest Italian hospital EDs are used