Will My Tests Tell Me If I Break This Code?

Automated tests play an important role in software evolution because they can rapidly detect faults introduced during changes. In practice, code-coverage metrics are often used as criteria to evaluate the effectiveness of test suites with focus on regression faults. However, code coverage only expresses which portion of a system has been executed by tests, but not how effective the tests actually are in detecting regression faults. Our goal was to evaluate the validity of code coverage as a measure for test effectiveness. To do so, we conducted an empirical study in which we applied an extreme mutation testing approach to analyze the tests of open-source projects written in Java. We assessed the ratio of pseudo-tested methods (those tested in a way such that faults would not be detected) to all covered methods and judged their impact on the software project. The results show that the ratio of pseudo-tested methods is acceptable for unit tests but not for system tests (that execute large portions of the whole system). Therefore, we conclude that the coverage metric is only a valid effectiveness indicator for unit tests.Comment: 7 pages, 3 figure

Screening properties and plasmons of Hg(Cd)Te quantum wells

Under certain conditions, Hg(Cd)Te quantum wells (QWs) are known to realize a time-reversal symmetric, two-dimensional topological insulator phase. Its low-energy excitations are well-described by the phenomenological Bernevig-Hughes-Zhang (BHZ) model that interpolates between Schr\"odinger and Dirac fermion physics. We study the polarization function of this model in random phase approximation (RPA) in the intrinsic limit and at finite doping. While the polarization properties in RPA of Dirac and Schr\"odinger particles are two comprehensively studied problems, our analysis of the BHZ model bridges the gap between these two limits, shedding light on systems with intermediate properties. We gain insight into the screening properties of the system and on its characteristic plasma oscillations. Interestingly, we discover two different kinds of plasmons that are related to the presence of intra- and interband excitations. Observable signatures of these plasmons are carefully analyzed in a variety of distinct parameter regimes, including the experimentally relevant ones for Hg(Cd)Te QWs. We conclude that the discovered plasmons are observable by Raman or electron loss spectroscopy

A frequency-selective feedback model of auditory efferent suppression and its implications for the recognition of speech in noise

The potential contribution of the peripheral auditory efferent system to our understanding of speech in a background of competing noise was studied using a computer model of the auditory periphery and assessed using an automatic speech recognition system. A previous study had shown that a fixed efferent attenuation applied to all channels of a multi-channel model could improve the recognition of connected digit triplets in noise [G. J. Brown, R. T. Ferry, and R. Meddis, J. Acoust. Soc. Am. 127, 943?954 (2010)]. In the current study an anatomically justified feedback loop was used to automatically regulate separate attenuation values for each auditory channel. This arrangement resulted in a further enhancement of speech recognition over fixed-attenuation conditions. Comparisons between multi-talker babble and pink noise interference conditions suggest that the benefit originates from the model?s ability to modify the amount of suppression in each channel separately according to the spectral shape of the interfering sounds

Do Heterogeneous Beliefs Matter for Asset Pricing?

We study how heterogeneous beliefs affect returns and examine whether heterogeneous beliefs are a priced factor in traditional asset pricing models. To accomplish this task, we suggest new empirical measures based on the disagreement among analysts about expected (short-term and long-term) earnings are good proxies. Having established that heterogeneity of beliefs matters for asset pricing we turn our attention to estimating a structural model in which we use the forecasts of financial analysts to proxy for the beliefs of agents. Finally, we investigate if the amount of heterogeneity in analysts' forecasts can help explain asset pricing puzzlesHeterogeneous Beliefs, Asset pricing

Video-Content auf Youtube-Kanälen von TV-Sendern am Beispiel von ARD, BBC und Deutsche Welle : Wahrnehmung, Nutzung und Wirkung von redaktionellen Video-Inhalten. Video content on Youtube channels of TV Stations with examples of ARD, BBC and Deutsche Welle : Perception, use and impact of Video with editorial content

This exploratory study is done to identify first assumptions for the use of video content in YouTube channels. A systematic process based on usage of video on-demand with perception, use and effect is used. The perception of video content can be viewed at several levels: the access, the design and the brand level. The use by the recipients concentrates on witch criteria videos are selected? How users navigate through the video? What elements of a website and a video will be seen during use? The effects focuses on cognitive, emotional and conative effects.Bewegtbildkommunikation, YouTube, Mediatheken, Eyetracking, Moving Image, YouTube, Usability, Eye Tracking, Media Library

On Applications of Disruption Tolerant Networking to Optical Networking in Space

The integration of optical communication links into space networks via Disruption Tolerant Networking (DTN) is a largely unexplored area of research. Building on successful foundational work accomplished at JPL, we discuss a multi-hop multi-path network featuring optical links. The experimental test bed is constructed at the NASA Glenn Research Center featuring multiple Ethernet-to-fiber converters coupled with free space optical (FSO) communication channels. The test bed architecture models communication paths from deployed Mars assets to the deep space network (DSN) and finally to the mission operations center (MOC). Reliable versus unreliable communication methods are investigated and discussed; including reliable transport protocols, custody transfer, and fragmentation. Potential commercial applications may include an optical communications infrastructure deployment to support developing nations and remote areas, which are unburdened with supporting an existing heritage means of telecommunications. Narrow laser beam widths and control of polarization states offer inherent physical layer security benefits with optical communications over RF solutions. This paper explores whether or not DTN is appropriate for space-based optical networks, optimal payload sizes, reliability, and a discussion on security

A catchment-based study of endocrine disruption in surface waters: multivariate evaluation of the health of a sentinel fish species exposed to sewage treatment works effluent

Summary of the results in the context of EDCAT 5 project aims: 1. By comparing appropriate biomarkers in fish sampled from STW-impacted sites and control sites during the pre-remediation period, to determine whether there was evidence for any effects that might be attributed to the presence of estrogenic (or androgenic, or anti-androgenic/-estrogenic) endocrine disrupting chemicals in the former. This aim was addressed by measuring concentrations of the estrogen-dependent yolk protein precursor vitellogenin, and the androgen-dependent nest glue spiggin in male and female sticklebacks. In addition histological examination of the gonadal structure of fish captured at the impacted and non-impacted sites was employed to seek evidence of overt alterations in reproductive physiology of the fish. For a subset of matched samples from the two rivers, the relative induction of hepatic choriogenin mRNA, a biomarker of estrogen exposure, was measured. Conclusions: Chemistry data provided by EDCAT3&4 showed that estrogenicity of the effluent was low prior to remediation and lower still following installation of the GAC plant. No evidence of overt estrogenic effects was detected in male sticklebacks in the Ray, VTG and ChG levels were similar in males from both rivers. Nor was there any evidence of alterations in spiggin concentrations in the kidneys of males from the Ray compared to the Ock. However, VTG concentrations in female sticklebacks from the Ray were increased following the STW upgrade as were hepatic ChG transcript levels, and kidney spiggin concentrations. No changes in these elements of the reproductive system were observed in females from the Ock across the same time periods. Chemical analysis of the effluent indicated that prior to installation of the GAC plant substantial concentrations of anti-androgenic chemicals were present, together with a wide range of other organics. Concentrations of these were much reduced following the plant upgrade. It is reasonable to suppose that the changes observed in the female reproductive endocrine system following the upgrade were related to the removal of some or all of this complex mixture of chemicals. The absence of effects in males may be related to the balance between exogenous and endogenous signals, or to the specificity of effects exerted by the chemicals present. No intersex fish were detected from either river. A significant bias in favour of females was detected in the stickleback populations in both rivers suggesting a factor associated with life-history of the fish, rather than contaminant burden, was responsible. 2. By comparing appropriate biomarkers in fish sampled from STW-impacted sites and control sites during the pre-remediation period, to determine whether there was evidence for any effects that might be attributed to the presence of “conventionally” toxic chemicals. This was addressed by measurement of the activity of a key Phase I transforming enzyme in the liver of fish, either using direct enzymatic assay (EROD) or by quantifying the levels of expression of the corresponding gene (CYP1A). Conclusions: EROD activity was significantly greater in fish from the Ray than the Ock in two samples collected prior to the installation of the GAC plant (2006, 2007) and this likely reflects the differential contaminant loading in the two rivers. A single sample following the commissioning of the GAC plant (2008) indicated that EROD activity had increased among fish from the Ock while that in fish from the Ray remained unchanged. While a delayed recovery of this biomarker in fish from the Ray may be expected depending on the route of exposure (direct via water or indirect via contaminated food) the reasons for elevated EROD activity in fish from the Ock/Childrey Brook are not immediately evident. Provision of a full data set for Cyp1A expression awaits the repeat of the assay. When this is complete the factors underlying the EROD findings may become clear. 3. To determine whether the adaptive capacity and energetic status of fish varied between the STW-impacted and non-impacted sites. This was addressed by measurement of indicators of stress (whole-body corticosteroid levels), metabolic status (whole-body glucose levels) and anabolic activity (RNA:DNA ratios). Conclusions: The data provide no evidence that the stress response of fish captured in the Ray prior to installation of the GAC plant was modified by exposure to the effluent. However, large variations in whole-body corticosteroid and glucose concentrations in fish from both rivers, with clear trends over time, were closely linked to perturbations in the river flow regime. Whether there was interaction between environmental and chemical factors in determining corticosteroid and glucose status is difficult to discern but it seems likely that variation in these indicators of the stress axis was driven primarily by environmental factors. The RNA:DNA ratios were closely linked with seasonal change in temperature and closely matched observed patterns of weight and length gain in stickleback populations in the two rivers. The longer growth period enjoyed by fish in the Ray was clearly evident. For both rivers, mean anabolic activity was greater during 2008 than 2007 and it seems likely that this is related to adverse effects associated with the periods of extreme flow change observed on both rivers in 2007. 4. To assess whether there were differences in population size and structure between STW-impacted and non-impacted sites. This was addressed by comparison of key somatic measures, in particular frequency distributions for fork length. Conclusions: Because of the extreme patchiness of the distribution of stickleback populations in both rivers accurate abundance estimates were not obtained. However, the catch per unit effort across the life of the project was similar for both rivers. While population size, and age structure (both rivers hosted annual populations), appeared to be similar fish in the Ray were overall larger than those from the Ock, and spawned earlier. The differences in growth and timing of spawning between the rivers were likely to have been associated with the Rodbourne STW effluent. Downstream of the discharge on the Ray water temperatures were consistently 2 – 3oC above those of the Ock. This temperature difference, in combination with the introduction of additional nutrients into the river which is likely to have affected the availaibility of food, probably accounts for the different growth profile among the sticklebacks in the two rivers. However, over and above this difference, there was a significant increase in size of sticklebacks in the Ray between the matched pre- and post-remediation periods in the Ray while no change in size of the fish in the Ock occurred during the same period. Similarly, the RNA:DNA ratio was higher in fish from the Ock during 2007 but greater in fish from the Ray during 2008. Taken together, these observations suggest that there was an improvement in the status of the fish in the Ray following the commissioning of the GAC plant, while the population in the Ock remained relatively stable. It is reasonable to suppose that this may be linked to the reduction of the chemical load entering the Ray at Rodbourne following the installation of the GAC plant. The Ray is “cleaner” now than was the case prior to remediation but remains nutrient rich and several degrees warmer than the Ock, this combination of factors providing fish in the Ray with greater scope for growth relative to populations in the Ock