Regularizing Image Reconstruction for Gradient-Domain Rendering with Feature Patches

We present a novel algorithm to reconstruct high-quality images from sampled pixels and gradients in gradient-domain rendering. Our approach extends screened Poisson reconstruction by adding additional regularization constraints. Our key idea is to exploit local patches in feature images, which contain per-pixels normals, textures, position, etc., to formulate these constraints. We describe a GPU implementation of our approach that runs on the order of seconds on megapixel images. We demonstrate a significant improvement in image quality over screened Poisson reconstruction under the L1 norm. Because we adapt the regularization constraints to the noise level in the input, our algorithm is consistent and converges to the ground truth.

Computer-based summative assessment of clinical reasoning in clerkships: A mixed-method comparison of key feature problems with case-based multiple choice questions

Background: It is yet unclear if there are differences between using electronic key feature problems (KFPs) or electronic case-based multiple choice questions (cbMCQ) for the assessment of clinical decision making. Summary of Work: Fifth year medical students were exposed to clerkships which ended with a summative exam. Assessment of knowledge per exam was done by 6-9 KFPs, 9-20 cbMCQ and 9-28 MC questions. Each KFP consisted of a case vignette and three key features (KF) using “long menu” as question format. We sought students’ perceptions of the KFPs and cbMCQs in focus groups (n of students=39). Furthermore statistical data of 11 exams (n of students=377) concerning the KFPs and (cb)MCQs were compared. Summary of Results: The analysis of the focus groups resulted in four themes reflecting students’ perceptions of KFPs and their comparison with (cb)MCQ: KFPs were perceived as (i) more realistic, (ii) more difficult, (iii) more motivating for the intense study of clinical reasoning than (cb)MCQ and (iv) showed an overall good acceptance when some preconditions are taken into account. The statistical analysis revealed that there was no difference in difficulty; however KFP showed a higher discrimination and reliability (G-coefficient) even when corrected for testing times. Correlation of the different exam parts was intermediate. Conclusions: Students perceived the KFPs as more motivating for the study of clinical reasoning. Statistically KFPs showed a higher discrimination and higher reliability than cbMCQs. Take-home messages: Including KFPs with long menu questions into summative clerkship exams seems to offer positive educational effects.

Computerbasierte Prüfung von klinischem Denken in der klinischen Ausbildung: Ein Mixed-Method Vergleich von Key Feature Problemen mit fallbasierten Multiple Choice Typ A Fragen

Fragestellung/Einleitung: Es ist unklar inwiefern Unterschiede bestehen im Einsatz von Key Feature Problemen (KFP) mit Long Menu Fragen und fallbasierten Typ A Fragen (FTA) für die Überprüfung des klinischen Denkens (Clinical Reasoning) in der klinischen Ausbildung von Medizinstudierenden. Methoden: Medizinstudierende des fünften Studienjahres nahmen an ihrer klinischen Pädiatrie-Rotation teil, die mit einer summativen Prüfung endete. Die Überprüfung des Wissen wurde pro Prüfung elektronisch mit 6-9 KFP [1], [3], 9-20 FTA und 9-28 nichtfallbasierten Multiple Choice Fragen (NFTA) durchgeführt. Jedes KFP bestand aus einer Fallvignette und drei Key Features und nutzen ein sog. Long Menu [4] als Antwortformat. Wir untersuchten die Perzeption der KFP und FTA in Focus Gruppen [2] (n of students=39). Weiterhin wurden die statistischen Kennwerte der KFP und FTA von 11 Prüfungen (n of students=377) verglichen. Ergebnisse: Die Analyse der Fokusgruppen resultierte in vier Themen, die die Perzeption der KFP und deren Vergleich mit FTA darstellten: KFP wurden als 1. realistischer, 2. schwerer, und 3. motivierender für das intensive Selbststudium des klinischen Denkens als FTA aufgenommen und zeigten 4. insgesamt eine gute Akzeptanz sofern gewisse Voraussetzungen berücksichtigt werden. Die statistische Auswertung zeigte keinen Unterschied im Schwierigkeitsgrad; jedoch zeigten die KFP eine höhere Diskrimination und Reliabilität (G-coefficient) selbst wenn für die Prüfungszeit korrigiert wurde. Die Korrelation der verschiedenen Prüfungsteile war mittel. Diskussion/Schlussfolgerung: Die Studierenden erfuhren die KFP als motivierenden für das Selbststudium des klinischen Denkens. Statistisch zeigten die KFP eine grössere Diskrimination und höhere Relibilität als die FTA. Der Einbezug von KFP mit Long Menu in Prüfungen des klinischen Studienabschnitts erscheint vielversprechend und einen „educational effect“ zu haben.

Regional surface morphology of comet 67P/Churyumov-Gerasimenko from Rosetta/OSIRIS images

Aims. The OSIRIS camera onboard the Rosetta spacecraft has been acquiring images of the comet 67P/Churyumov-Gerasimenko (67P)'s nucleus at spatial resolutions down to similar to 0.17 m/px ever since Aug. 2014. These images have yielded unprecedented insight into the morphological diversity of the comet's surface. This paper presents an overview of the regional morphology of comet 67P. Methods. We used the images that were acquired at orbits similar to 20-30 km from the center of the comet to distinguish different regions on the surface and introduce the basic regional nomenclature adopted by all papers in this Rosetta special feature that address the comet's morphology and surface processes. We used anaglyphs to detect subtle regional and topographical boundaries and images from close orbit (similar to 10 km from the comet's center) to investigate the fine texture of the surface. Results. Nineteen regions have currently been defined on the nucleus based on morphological and/or structural boundaries, and they can be grouped into distinctive region types. Consolidated, fractured regions are the most common region type. Some of these regions enclose smooth units that appear to settle in gravitational sinks or topographically low areas. Both comet lobes have a significant portion of their surface covered by a dusty coating that appears to be recently placed and shows signs of mobilization by aeolian-like processes. The dusty coatings cover most of the regions on the surface but are notably absent from a couple of irregular large depressions that show sharp contacts with their surroundings and talus-like deposits in their interiors, which suggests that short-term explosive activity may play a significant role in shaping the comet's surface in addition to long-term sublimation loss. Finally, the presence of layered brittle units showing signs of mechanical failure predominantly in one of the comet's lobes can indicate a compositional heterogeneity between the two lobes.

Who cares about my feature request?

Previous studies on issue tracking systems for open source software (OSS) focused mainly on requests for bug fixes. However, requests to add a new feature or an improvement to an OSS project are often also made in an issue tracking system. These inquiries are particularly important because they determine the further development of the software. This study examines if there is any difference between requests of the IBM developer community and other sources in terms of the likelihood of successful implementation. Our study consists of a case study of the issue tracking system BugZilla in the Eclipse integrated development environment (IDE). Our hypothesis, which was that feature requests from outsiders have less chances of being implemented, than feature requests from IBM developers, was confirmed.

Automatic Stabilizer Feature of Fixed Exchange Rate Regimes in Emerging Markets

This paper shows that countries characterized by a financial accelerator mechanism may reverse the usual finding of the literature -- flexible exchange rate regimes do a worse job of insulating open economies from external shocks. I obtain this result with a calibrated small open economy model that endogenizes foreign interest rates by linking them to the banking sector's foreign currency leverage. This relationship renders exchange rate policy more important compared to the usual exogeneity assumption. I find empirical support for this prediction using the Local Projections method. Finally, 2nd order approximation to the model finds larger welfare losses under flexible regimes.

Radiomics of NSCLC: Quantitative CT Image Feature Characterization and Tumor Shrinkage Prediction

Radiomics is the high-throughput extraction and analysis of quantitative image features. For non-small cell lung cancer (NSCLC) patients, radiomics can be applied to standard of care computed tomography (CT) images to improve tumor diagnosis, staging, and response assessment. The first objective of this work was to show that CT image features extracted from pre-treatment NSCLC tumors could be used to predict tumor shrinkage in response to therapy. This is important since tumor shrinkage is an important cancer treatment endpoint that is correlated with probability of disease progression and overall survival. Accurate prediction of tumor shrinkage could also lead to individually customized treatment plans. To accomplish this objective, 64 stage NSCLC patients with similar treatments were all imaged using the same CT scanner and protocol. Quantitative image features were extracted and principal component regression with simulated annealing subset selection was used to predict shrinkage. Cross validation and permutation tests were used to validate the results. The optimal model gave a strong correlation between the observed and predicted shrinkages with . The second objective of this work was to identify sets of NSCLC CT image features that are reproducible, non-redundant, and informative across multiple machines. Feature sets with these qualities are needed for NSCLC radiomics models to be robust to machine variation and spurious correlation. To accomplish this objective, test-retest CT image pairs were obtained from 56 NSCLC patients imaged on three CT machines from two institutions. For each machine, quantitative image features with concordance correlation coefficient values greater than 0.90 were considered reproducible. Multi-machine reproducible feature sets were created by taking the intersection of individual machine reproducible feature sets. Redundant features were removed through hierarchical clustering. The findings showed that image feature reproducibility and redundancy depended on both the CT machine and the CT image type (average cine 4D-CT imaging vs. end-exhale cine 4D-CT imaging vs. helical inspiratory breath-hold 3D CT). For each image type, a set of cross-machine reproducible, non-redundant, and informative image features was identified. Compared to end-exhale 4D-CT and breath-hold 3D-CT, average 4D-CT derived image features showed superior multi-machine reproducibility and are the best candidates for clinical correlation.

Physical properties and neutron texture measuerments of deep-sea carbonates of DSDP Holes 62-463 and 62-465A

In weakly indurated, nannofossil-rich, deep-sea carbonates compressional wave velocity is up to twice as fast parallel to bedding than normal to it. It has been suggested that this anisotropy is due to alignment of calcite c-axes perpendicular to the shields of coccoliths and shield deposition parallel to bedding. This hypothesis was tested by measuring the preferred orientation (fabric) of calcite c-axes in acoustic anisotropic, calcareous DSDP sediment samples by X-ray goniometry, and it was found that the maximum c-axis concentrations are by far too low to explain the anisotropies. The X-ray method is subject to a number of uncertainties due to preparatory and technical shortcomings in weakly indurated rocks. The most serious weaknesses are: sample preparation, volume of measured sample (fraction of a mm3), beam defocusing and background intensity corrections, combination of incomplete pole figures, and necessity of recalculation of the c-axis orientations from other crystallographic directions. Goniometry using thermal neutrons overcomes most of these difficulties, but it is time consuming. We test the interferences made about velocity anisotropy by X-ray studies about the concentration of c-axes in deep-sea carbonates by employing neutron texture goniometry to eight DSDP samples comprising mostly nannofossil material. Fabric and sonic velocity were determined directly on the core specimens, thus from the same rock volume and requiring no preparation. The c-axis orientation is obtained directly from the [0006] calcite diffraction peak without corrections. The fabrics are clearly defined, but weak (1.1 to 1.86 times uniform) with the maximum about normal to bedding. They have crudely orthorhombic symmetry, but are not axisymmetric around the bedding normal. The observed c-axis intensities, although higher than determined by the X-ray method on other samples, are by far too low to explain the observed acoustic anisotropies.

Analyses of shocked quartz from the K-P boundary

The precise cause and timing of the Cretaceous-Paleocene (K-P) mass extinction 65 Ma ago remains a matter of debate. Many advocate that the extinction was caused by a meteorite impact at Chicxulub, Mexico, and a number of potential kill-mechanisms have been proposed for this. Although we now have good constraints on the size of this impact and chemistry of the target rocks, estimates of its environmental consequences are hindered by a lack of knowledge about the obliquity of this impact. An oblique impact is likely to have been far more catastrophic than a sub-vertical one, because greater volumes of volatiles would have been released into the atmosphere. The principal purpose of this study was to characterize shocked quartz within distal K-P ejecta, to investigate whether the quartz distribution carried a signature of the direction and angle of impact. Our analyses show that the total number, maximum and average size of shocked quartz grains all decrease gradually with paleodistance from Chicxulub. We do not find particularly high abundances in Pacific sites relative to Atlantic and European sites, as has been previously reported, and the size-distribution around Chicxulub is relatively symmetric. Ejecta samples at any one site display features that are indicative of a wide range of shock pressures, but the mean degree of shock increases with paleodistance. These shock- and size-distributions are both consistent with the K-P layer having been formed by a single impact at Chicxulub. One site in the South Atlantic contains quartz indicating an anomalously high average shock degree, that may be indicative of an oblique impact with an uprange direction to the southeast +/- 45°. The apparent continuous coverage of proximal ejecta in this quadrant of the crater, however, suggests a relatively high impact angle of >45°. We conclude that some of the more extreme predictions of the environmental consequences of a low-angle impact at Chicxulub are probably not applicable.

Geochemical composition and crystallization temperatures of ODP Hole 176-735B gabbroic rocks

The transition from magmatic crystallization to high-temperature metamorphism in deep magma chambers (or lenses) beneath spreading ridges has not been fully described. High-temperature microscopic veins found in olivine gabbros, recovered from Ocean Drilling Program Hole 735B on the Southwest Indian Ridge during Leg 176, yield information on the magmatic-hydrothermal transition beneath spreading ridges. The microscopic veins are composed of high-temperature minerals, (i.e., clinopyroxene, orthopyroxene, brown amphibole, and plagioclase). An important feature of these veins is the 'along-vein variation' in mineralogy, which is correlated with the magmatic minerals that they penetrate. Within grains of magmatic plagioclase, the veins are composed of less calcic plagioclase. In grains of olivine, the veins are composed of orthopyroxene + brown amphibole + plagioclase. In clinopyroxene grains, the veins consist of plagioclase + brown amphibole and are accompanied by an intergrowth of brown amphibole + orthopyroxene. The mode of occurrence of the veins cannot be explained if these veins were crystallized from silicate melts. Consequently, these veins and nearby intergrowths were most likely formed by the reaction of magmatic minerals with fluid phases under the conditions of low fluid/rock ratios. Very similar intergrowths of brown amphibole + orthopyroxene are observed in clinopyroxene grains with 'interfingering' textures. It is believed, in general, that the penetration of seawater does not predate the ductile deformation within Layer 3 gabbros of the slow-spreading ridges. If this is the case, the fluid responsible for the veins did not originate from seawater because the formation of the veins and the interfingering textures preceded ductile deformation and, perhaps, complete solidification of the gabbroic crystal mush. It has been proposed, based on fluid inclusion data, that the exsolution of fluid from the latest-stage magma took place at temperatures >700°C in the slow-spreading Mid-Atlantic Ridge at the Kane Fracture Zone (MARK) area. No obvious mineralogical evidence, however, has been found for these magmatic fluids. The calculated temperatures for the veins and nearby intergrowths found in Hole 735B gabbros are up to 1000°C, and these veins are the most plausible candidate for the mineralogical expression of the migrating magmatic fluids.

Texture, geochemistry, isotope composition, petrography and epoch at DSDP Site 93-603

Abundant Fe-Mn carbonate concretions (mainly siderite, manganosiderite, and rhodochrosite) were found in the hemipelagic claystones of Site 603 on the eastern North American continental rise. They occur as nodules, micronodules, or carbonate-replaced burrow fills and layers at a subbottom depth of between ~ 120 (Pliocene) and 1160 m (Albian-Cenomanian). In general, the Fe-Mn carbonate concretions form from CO3- produced by the microbiological degradation of organic matter in the presence of abundant Fe + or Mn + and very low S- concentrations. However, there is also some evidence for diagenetic replacement of preexisting calcite by siderite. The carbon isotope composition of diagenetic Fe-Mn carbonate nodules is determined by CO2 reduction during methanogenesis. Carbonate nodules in Cretaceous sediments at sub-bottom depths of 1085 and 1160 m have distinctly lower d13C values (- 12.2 and - 12.9 per mil) than Neogene siderites, associated with abundant biogenic methane in the pore space (-8.9 to 1.7 per mil between 330 and 780 m depth). Since no isotopic zonation could be detected within individual nodules, we assume that the isotopic composition reflects more or less geochemical conditions at the present burial depth of the carbonate nodules. Carbonates did not precipitate within the zone of sulfate reduction (approximately 0.01 to 10 m), where all of the pyrite was formed. The oxygen isotope composition indicates precipitation from seawater-derived interstitial waters. The d18O values decrease with increasing burial depth from + 5.1 to - 1.2 per mil, suggesting successively higher temperatures during carbonate formation.

Sediment texture, carbonate content, and carbonate mineralogy of ODP Holes 182-1130A and 182-1132B

At Sites 1130 and 1132 of Ocean Drilling Program Leg 182 in the Great Australian Bight, we recovered an expanded Pleistocene section dominated by packstone and wackestone, deposited at unusually high rates of >20 cm/k.y. Shipboard observations detected an intermittent meter-scale alternation of light gray intervals with olive-gray intervals. Meter-scale samples were collected from the upper 250 m at both sites and decimeter-scale samples from four selected 2.5- to 4.0-m intervals in order to determine the texture and composition of sediments deposited along the upper slope throughout the Quaternary. Detailed textural and compositional data are presented from a total of 540 samples collected from both sites. Results indicate a general coarsening upward at both sites, with an accompanying upcore increase in high-Mg calcite (HMC) and aragonite and a decrease in low-Mg calcite (LMC). Samples collected at decimeter-scale intervals substantiate that the alternating light gray and olive-gray units detected on board ship are lithologically distinct. Light gray units consist of an LMC-rich silt, whereas olive-gray units consist of an aragonite and HMC-rich sand and silt. Sediment sources as well as timing and controls of this cyclic depositional pattern will be the subject of further investigations.