Adaptive correlations between seed size and germination time

We present a model for the coevolution of seed size and germination time within a season when both affect the ability of the seedlings to compete for space. We show that even in the absence of a morphological or physiological constraint between the two traits, a correlation between seed size and germination time is nevertheless likely to evolve. This raises the more general question to what extent a correlation between any two traits should be considered as an a priori constraint or as an evolved means (or instrument) to actually implement a beneficial combination of traits. We derive sufficient conditions for the existence of a positive or a negative correlation. We develop a toy model for seed and seedling survival and seedling growth and use this to illustrate in practice how to determine correlations between seed size and germination time.Peer reviewe

Self-assembled GaIn(N)As quantum dots: Enhanced luminescence at 1.3 µm

Self-assembled GaIn(N)As quantum dots are fabricated on GaAs by atmospheric pressuremetalorganic vapor-phase epitaxy using dimethylhydrazine (DMHy) precursor as a nitrogen source. The incorporation of nitrogen into the islands is observed to be negligible. However, the areal density of the islands is increased by up to one order of magnitude compared to that of the respective GaInAs islands. The GaIn(N)As island size can also be controlled by varying the DMHy flow. An enhancement of the room-temperature luminescence at 1.3 μm is observed in the GaIn(N)As samples grown with DMHy.Peer reviewe

List-mode data acquisition based on digital electronics - State-of-the-art report

This report deals with digital radiation detection systems employing list-mode data collection, which improves data analysis capabilities. Future data acquisition systems shall also ultimately enable the movement of detection data from first responders electronically to analysis centres rather than the costly and time consuming process of moving experts and/or samples. This new technology is especially useful in crisis events, when time and resources are sparse and increased analysis capacity is required. In order to utilise the opportunities opened by these new technologies, the systems have to be interoperable, so that the data from each type of detector can easily be analysed by different analysis centres. Successful interoperability of the systems requires that European and/or international standards are devised for the digitised data format. The basis of such a format is a list of registered events detailing an estimate of the energy of the detected radiation, along with an accurate time-stamp for recorded events (and optionally other parameters describing each event).JRC.G.5-Security technology assessmen

Experimental investigation towards a periodically pumped single-photon source

Experiments towards a periodically pumped single-photon source are presented. The lateral piezoelectric field of a surface acoustic wave dissociates laser-generated two-dimensional excitons into electrons and holes. These carriers are separated by the wave potential and are transported over macroscopic length scales without recombining. When reaching a stress-induced quantum dot in the quantum well they periodically populate the zero-dimensional states and recombine, emitting single photons periodically in time according to the surface acoustic-wave frequency. We have successfully reduced the number of pumped quantum dots down to 100 and have detected a strong blinking photoluminescence signal. By further reducing the number of quantum dots down to 1 a periodically pumped single photon source could be realized.Peer reviewe

Observation of defect complexes containing Ga vacancies in GaAsN

Positron annihilation spectroscopy was used to study GaAsN/GaAs epilayers. GaAsN layers were found to contain Ga vacancies in defect complexes. The density of the vacancy complexes increases rapidly to the order of 1018 cm−3 with increasing N composition and decreases after annealing at 700 °C. The anticorrelation of the vacancy concentration and the integrated photoluminescence intensity suggests that the Ga vacancy complexes act as nonradiative recombination centers.Peer reviewe

Anomalous lifetime distributions and topological traps in ordering dynamics

We address the role of community structure of an interaction network in ordering dynamics, as well as associated forms of metastability. We consider the voter and AB model dynamics in a network model which mimics social interactions. The AB model includes an intermediate state between the two excluding options of the voter model. For the voter model we find dynamical metastable disordered states with a characteristic mean lifetime. However, for the AB dynamics we find a power law distribution of the lifetime of metastable states, so that the mean lifetime is not representative of the dynamics. These trapped metastable states, which can order at all time scales, originate in the mesoscopic network structure.Comment: 7 pages; 6 figure

Performance of Surgical Stress Index during Sevoflurane-Fentanyl and Isoflurane-Fentanyl Anesthesia

The performance of recently introduced Surgical Stress Index (SSI), based on heart rate and photoplethysmography, was estimated during sevoflurane-fentanyl and isoflurane-fentanyl anesthesia during surgical procedures. Forty ASA I–III patients were enrolled. Anesthesia was induced with fentanyl 2 μg kg−1 and thiopentone 3–5 mg kg−1. Tracheal intubation was performed 5 minutes after fentanyl bolus. Patients were randomly allocated to receive sevoflurane (n = 20) or isoflurane (n = 20) in 30% oxygen/air. State entropy was kept at 40–60, target being 50. During surgery, fentanyl boluses 1.5 μg kg−1 were given at 30–40-minute intervals. SSI increased significantly after intubation. During surgery, the decrease of SSI after fentanyl boluses was similar in sevoflurane and isoflurane groups but SSI values were higher in sevoflurane than in isoflurane group. Tracheal intubation, skin incision, and surgical stimuli increased SSI from baseline, indicating that nociceptive stimuli increase SSI. Fentanyl boluses during surgery decreased SSI, indicating that increasing analgesia decreases SSI

Critical parameters and performance tests for the evaluation of digital data acquisition hardware

Recent developments of digital data acquisition systems allow real-time pre-processing of detector signals at a high count rate. These so-called pulse processing digitizers are powerful and versatile instruments offering techniques which are important for nuclear security, critical infrastructure protection, nuclear physics and radiation metrology. Certain aspects of digital data acquisition affect the performance of the total system in a critical way and therefore require special attention. This report presents a short introduction to digital data acquisition, followed by a discussion of the critical parameters which affect the performance in the lab and in the field. For some of the parameters, tests are proposed to assess the performance of digital data acquisition systems. Good practices are offered to guide the selection and evaluation of digital data acquisition systems. More general performance criteria which are not specifically related to digital data acquisition systems are discussed separately.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard