3,548 research outputs found
The Danger of Incorrect Expectations In Driving: The Failure to Respond
This paper addresses Inattentional Blindness or look-but-fail-to-see in driving. How it is possible that visual information, highly relevant for driving is not perceived or responded to. Our main focus was on driver expectations. Different experimental studies were performed. In the conducted studies, we had drivers perform a driving task in which they had to drive a specific road numerous times. This way they were able to control driver expectations with a specific road environment. After some drives we made some crucial changes to the road environment (e.g., change in priority, change in No-Entry road). Behavioural responses (speed, deceleration) were measured to these changes, as well as eye movenents (glance duration) and awareness of the changes. All partcipants were experienced drivers, and over all studies, 250 drivers participated. There was a relation between driver expectations and the failure to respond. Glance duration to traffic signs was found to decrease with a driver becoming more and more familiar with a specific road. Visually selecting the information seems to be an important condition for enabling a response, but it is certainly not enough. There are various cases where expectations were so strong that drivers looked at the information but did not respond. There seems to be a high correlation between glance duration and responding, as well as between the type of change and responding. In-vehicle equipment warning the driver for these types of situations is highly effective. An elaborated task performance model is presented
Forecasting Sovereign Default risk with Mertonâs Model
Merton's structural model for sovereigns is proven to be useful to analyze the default risk of a country. We are the first to investigate how fast CDS spreads react to changes in model inputs and outputs. CDS spread changes strongly correlate with exchange rate returns, which are an input to the model. But CDS spread changes on average react with a delay to changes in model outputs such as the distance to default, the default probability and model spreads. Hence contingency claim analysis for sovereigns provides useful predictions for CDS spreads
Potential of Forages in Crop Diversification and Crop Rotation
Redesign of agricultural systems according to ecological principles has been proposed for the development of sustainable systems. We review a wide variety of ecologically-based crop production practices that focus on forage crops in farming systems and discuss their potential role in enhancing the profitability, environmental sustainability and resilience. Crop-livestock systems that most closely mimic natural systems through appropriate integration of diverse components appear to offer the greatest potential benefits. These systems are more energy efficient and combine high productivity with low ecological footprint. Greater understanding of ecological relationships within crop-livestock systems are required to purposefully and proactively redesign agricultural systems for profitability, sustainability and resilience
Measuring volatility with the realized range
Realized variance, being the summation of squared intra-day returns,
has quickly gained popularity as a measure of daily volatility.
Following Parkinson (1980) we replace each squared intra-day return
by the high-low range for that period to create a novel and more
efficient estimator called the realized range. In addition we
suggest a bias-correction procedure to account for the effects of
microstructure frictions based upon scaling the realized range with
the average level of the daily range. Simulation experiments
demonstrate that for plausible levels of non-trading and bid-ask
bounce the realized range has a lower mean squared error than the
realized variance, including variants thereof that are robust to
microstructure noise. Empirical analysis of the S&P500
index-futures and the S&P100 constituents confirm the potential of
the realized range
A personal, distributed exposimeter: procedure for design, calibration, validation, and application
This paper describes, for the first time, the procedure for the full design, calibration, uncertainty analysis, and practical application of a personal, distributed exposimeter (PDE) for the detection of personal exposure in the Global System for Mobile Communications (GSM) downlink (DL) band around 900 MHz (GSM 900 DL). The PDE is a sensor that consists of several body-worn antennas. The on-body location of these antennas is investigated using numerical simulations and calibration measurements in an anechoic chamber. The calibration measurements and the simulations result in a design (or on-body setup) of the PDE. This is used for validation measurements and indoor radio frequency (RF) exposure measurements in Ghent, Belgium. The main achievements of this paper are: first, the demonstration, using both measurements and simulations, that a PDE consisting of multiple on-body textile antennas will have a lower measurement uncertainty for personal RF exposure than existing on-body sensors; second, a validation of the PDE, which proves that the device correctly estimates the incident power densities; and third, a demonstration of the usability of the PDE for real exposure assessment measurements. To this aim, the validated PDE is used for indoor measurements in a residential building in Ghent, Belgium, which yield an average incident power density of 0.018 mW/m(2)
Determination of Sapphire OffâCut and Its Influence on the Morphology and Local Defect Distribution in Epitaxially Laterally Overgrown AlN for Optically Pumped UVC Lasers
Herein, a systematic study of the morphology and local defect distribution in epitaxially laterally overgrown (ELO) AlN on câplane sapphire substrates with different offâcut angles ranging from 0.08° to 0.23° is presented. Precise measurements of the offâcut angle α, using a combination of optical alignment and Xâray diffraction with an accuracy of ±5° for the offâcut direction and ±0.015° for the offâcut angle, are carried out. For ELO AlN growth, a transition from step flow growth at αââ0.14° is observed. Furthermore, the terraces of the stepâbunched surface exhibit curved steps. An analysis of the local defect distribution by scanning transmission electron microscopy and a comparison with atomic force microscopy reveal a bunching of defects in line with the ELO pattern and a roughening of step edges in highly defective regions. In addition, a reduction in the threshold excitation power density for optically pumped ultravioletâC (UVC) lasers with smooth surface morphologies is observed.TU Berlin, Open-Access-Mittel - 201
Functional analysis of ATM and ATR in the moss Physcomitrella patens
Homologous recombination (HR) is an essential biological process, which plays a pivotal role in mechanisms such as meiotic crossover and the reparation of DNA double strand breaks. In addition to being a fundamental process of life, it is also the basis of gene targeting, a technical application, which utilizes the cells HR apparatus for precise genome editing. While GT has been successfully employed for functional genome analysis in mice and yeast, higher plants are innately inefficient in GT. This is because they repair DNA double strand breaks preferentially with another pathway, non homologous end joining (NHEJ), which does not lead to targeted insertions. On the other hand, the moss Physcomitrella patens preferentially uses HR for DSB repair as well as transgene integration. This feature makes P. patens a suitable model organism for studying HR in general, which could also provide a better understanding of its outstanding GT properties.
In order to extend our knowledge on this subject, the present thesis focused on two major topics. In the first part the inventory of DNA repair and recombination genes in P. patens was assessed via a BLAST based approach, which was made possible by the recent release of the P. patens genome draft. Intriguingly, P. patens possesses all important NHEJ genes, therefore its bias for HR over NHEJ could not be explained based on simple presence or absence of known NHEJ genes. On the other hand, there were similarities regarding the absence/presence of HR genes between P. patens and the also highly HR biased and GT efficient yeast. For example, BRCA1, BRCA2 and BARD1 are neither found in P. patens nor in yeast. Even more intriguingly they are available in Arabidopsis and also humans, where NHEJ is the dominant pathway. A further remarkable observation was that for 33 of the DNA repair and recombination related genes available in P. patens additional paralogs were identified. These paralogs are certainly interesting candidates for further studies.
The second part of the thesis focused on the ATM (ataxia telangiectasia mutated) and ATR (ATM and Rad3-related) kinases, two key upstream signaling components of HR mediated DNA DSB repair. Utilizing the proficiency of P. patens in gene targeting ATM and ATR single as well as double mutants were generated by disrupting their kinase domains. These mutants were then used to characterize the function of the P. patens ATM and ATR homologs. Observing the mutant lines it was found that the loss of ATR function severely compromised vegetative and reproductive development while ATM disruption had just a mild effect on vegetative development. Testing the sensitivity of the mutant lines to various DNA DSB inducing agents it was found that in P. patens mainly ATR is required to facilitate the repair of these lesions, a situation similar to yeast but different to human cells and Arabidopsis, where also loss of ATM markedly affects sensitivity to these genotoxic agents. Similarly, another response to DNA DSB, the arrest of the cell cycle is also mediated by largely ATR in P. patens as well as yeast, while in Arabidopsis and human cells ATM also plays an important role. As part of the mutant phenotype analysis, the effect of ATM and ATR loss of function on the mode of transgene integration was tested. It was found that removal of ATM function significantly increased NHEJ mediated random integrations while targeted integrations were unaffected, the latter were reduced only in the ATM and ATR double mutant.
Another major part of the thesis was to assess the global transcriptional change in response to bleomycin mediated DNA DSB induction in wild type as well as in mutant lines. Although P. patens is known to be biased towards HR, unexpectedly, in addition to HR genes also NHEJ genes were found transcriptionally induced in the wild type. Comparing the transcriptomes of wild type and mutant lines large differences in transcript levels were already observed without bleomycin treatment. Additional bleomycin treatment showed that a large number of DNA damage responsive transcripts could not be induced or repressed in the mutant lines. Another interesting finding was that while the transcriptional DNA damage response in Arabidopsis appears to largely rely on ATM function, in P. patens ATR seem to be more important in this regard
Robust Optimization of the Equity Momentum Strategy
Quadratic optimization for asset portfolios often leads to error maximization, with optimizers zooming in on large errors in the predicted inputs, that is, expected returns and risks. The consequence in most cases is a poor real-time performance. In this paper we show how to improve real-time performance of the popular equity momentum strategy with robust optimization in an empirical application involving 1500-2500 US stocks over the period 1963-2006. We also show that popular procedures like Bayes-Stein estimated expected returns, shrinking the covariance matrix and adding weight constraints fail in such a practical case
Residual Momentum
Conventional momentum strategies exhibit substantial time-varying exposures to the Fama and French factors. We show that these exposures can be reduced by ranking stocks on residual stock returns instead of total returns. As a consequence, residual momentum earns risk-adjusted profits that are about twice as large as those associated with total return momentum; is more consistent over time; and less concentrated in the extremes of the cross-section of stocks. Our results are inconsistent with the notion that the momentum phenomenon can be attributed to a priced risk factor or market microstructure effects
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