bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sequential Monte Carlo Adaptation in Low‐Anisotropy Participating Media
Authors: Pegoraro Vincent , Wald Ingo , Parker Steven G. 
Published: September 2008

AbstractThis paper presents a novel method that effectively combines both control variates and importance sampling in a sequential Monte Carlo context. The radiance estimates computed during the rendering process are cached in a 5D adaptive hierarchical structure that defines dynamic predicate functions for both variance reduction techniques and guarantees well‐behaved PDFs, yielding continually increasing efficiencies thanks to a marginal computational overhead. While remaining unbiased, the technique is effective within a single pass as both estimation and caching are done online, exploiting the coherency in illumination while being independent of the actual scene representation. The method is relatively easy to implement and to tune via a single parameter, and we demonstrate its practical benefits with important gains in convergence rate and competitive results with state of the art techniques.
Table‐driven Adaptive Importance Sampling
Authors: Cline David , Adams Daniel , Egbert Parris 
Published: September 2008

AbstractMonte Carlo rendering algorithms generally rely on some form of importance sampling to evaluate the measurement equation. Most of these importance sampling methods only take local information into account, however, so the actual importance function used may not closely resemble the light distribution in the scene. In this paper, we present Table‐driven Adaptive Importance Sampling (TAIS), a sampling technique that augments existing importance functions with tabular importance maps that direct sampling towards undersampled regions of path space. The importance maps are constructed lazily, relying on information gathered during the course of sampling. During sampling the importance maps act either in parallel with or as a preprocess to existing importance sampling methods. We show that our adaptive importance maps can be effective at reducing variance in a number of rendering situations.
Exploiting Visibility Correlation in Direct Illumination
Authors: Clarberg Petrik , Akenine‐Möller Tomas 
Published: September 2008

AbstractThe visibility function in direct illumination describes the binary visibility over a light source, e.g., an environment map. Intuitively, the visibility is often strongly correlated between nearby locations in time and space, but exploiting this correlation without introducing noticeable errors is a hard problem. In this paper, we first study the statistical characteristics of the visibility function. Then, we propose a robust and unbiased method for using estimated visibility information to improve the quality of Monte Carlo evaluation of direct illumination. Our method is based on the theory of control variates, and it can be used on top of existing state‐of‐the‐art schemes for importance sampling. The visibility estimation is obtained by sparsely sampling and caching the 4D visibility field in a compact bitwise representation. In addition to Monte Carlo rendering, the stored visibility information can be used in a number of other applications, for example, ambient occlusion and lighting design.
Stylized Vector Art from 3D Models with Region Support
Authors: Eisemann Elmar , Winnemöller Holger , Hart John C. , Salesin David 
Published: September 2008

AbstractWe describe a rendering system that converts a 3D meshed model into the stylized 2D filled‐region vector‐art commonly found in clip‐art libraries. To properly define filled regions, we analyze and combine accurate but jagged face‐normal contours with smooth but inaccurate interpolated vertex normal contours, and construct a new smooth shadow contour that properly surrounds the actual jagged shadow contour. We decompose region definition into geometric and topological components, using machine precision for geometry processing and raster‐precision to accelerate topological queries. We extend programmable stylization to simplify, smooth and stylize filled regions. The result renders 10K‐face meshes into custom clip‐art in seconds.
Shallow Bounding Volume Hierarchies for Fast SIMD Ray Tracing of Incoherent Rays
Authors: Dammertz H. , Hanika J. , Keller A. 
Published: September 2008

AbstractPhotorealistic image synthesis is a computationally demanding task that relies on ray tracing for the evaluation of integrals. Rendering time is dominated by tracing long paths that are very incoherent by construction. We therefore investigate the use of SIMD instructions to accelerate incoherent rays. SIMD is used in the hierarchy construction, the tree traversal and the leaf intersection. This is achieved by increasing the arity of acceleration structures, which also reduces memory requirements. We show that the resulting hierarchies can be built quickly and are smaller than acceleration structures known so far while at the same time outperforming them for incoherent rays. Our new acceleration structure speeds up ray tracing by a factor of 1.6 to 2.0 compared to a highly optimized bounding interval hierarchy implementation, and 1.3 to 1.6 compared to an efficient kd‐tree. At the same time, the memory requirements are reduced by 10–50%. Additionally we show how a caching mechanism in conjunction with this memory efficient hierarchy can be used to speed up shadow rays in a global illumination algorithm without increasing the memory footprint. This optimization decreased the number of traversal steps up to 50%.
ScribbleBoost: Adding Classification to Edge‐Aware Interpolation of Local Image and Video Adjustments
Authors: Li Y. , Adelson E. , Agarwala A. 
Published: September 2008

AbstractOne of the most common tasks in image and video editing is the local adjustment of various properties (e.g., saturation or brightness) of regions within an image or video. Edge‐aware interpolation of user‐drawn scribbles offers a less effort‐intensive approach to this problem than traditional region selection and matting. However, the technique suffers a number of limitations, such as reduced performance in the presence of texture contrast, and the inability to handle fragmented appearances. We significantly improve the performance of edge‐aware interpolation for this problem by adding a boosting‐based classification step that learns to discriminate between the appearance of scribbled pixels. We show that this novel data term in combination with an existing edge‐aware optimization technique achieves substantially better results for the local image and video adjustment problem than edge‐aware interpolation techniques without classification, or related methods such as matting techniques or graph cut segmentation.
Fast Soft Self‐Shadowing on Dynamic Height Fields
Authors: Snydre John , Nowrouzezahrai Derek 
Published: September 2008

AbstractWe present a new, real‐time method for rendering soft shadows from large light sources or lighting environments on dynamic height fields. The method first computes a horizon map for a set of azimuthal directions. To reduce sampling, we compute a multi‐resolution pyramid on the height field. Coarser pyramid levels are indexed as the distance from caster to receiver increases. For every receiver point and every azimuthal direction, a smooth function of blocking angle in terms of log distance is reconstructed from a height difference sample at each pyramid level. This function's maximum approximates the horizon angle. We then sum visibility at each receiver point over wedges determined by successive pairs of horizon angles. Each wedge represents a linear transition in blocking angle over its azimuthal extent. It is precomputed in the order‐4 spherical harmonic (SH) basis, for a canonical azimuthal origin and fixed extent, resulting in a 2D table. The SH triple product of 16D vectors representing lighting, total visibility, and diffuse reflectance then yields the soft‐shadowed result. Two types of light sources are considered; both are distant and low‐frequency. Environmental lights require visibility sampling around the complete 360 ° azimuth, while key lights sample visibility within a partial swath. Restricting the swath concentrates samples where the light comes from (e.g. 3 azimuthal directions vs. 16‐32 for a full swath) and obtains sharper shadows. Our GPU implementation handles height fields up to 1024 × 1024 in real‐time. The computation is simple, local, and parallel, with performance independent of geometric content.
ReduceM: Interactive and Memory Efficient Ray Tracing of Large Models
Authors: Lauterbach Christian , Yoon Sung‐eui , Tang Ming , Manocha Dinesh 
Published: September 2008

AbstractWe present a novel representation and algorithm, ReduceM, for memory efficient ray tracing of large scenes. ReduceM exploits the connectivity between triangles in a mesh and decomposes the model into triangle strips. We also describe a new stripification algorithm, Strip‐RT, that can generate long strips with high spatial coherence. Our approach uses a two‐level traversal algorithm for ray‐primitive intersection. In practice, ReduceM can significantly reduce the storage overhead and ray trace massive models with hundreds of millions of triangles at interactive rates on desktop PCs with 4‐8GB of main memory.
Hansen's disease in a general hospital: uncommon presentations and delay in diagnosis
Authors: Da Costa Nery JA , Schreuder PAM , Castro Teixeira de Mattos P , Vieira de Mendonça L , Tebaldi Tardi R , De Mello S , Azulay RD , Lehman LF , Naafs B 
Published: September 2008

AbstractBackground  The question was raised as to why ‘obvious’ signs of leprosy, Hansen's disease (HD), are often missed by medical doctors working in a HD endemic area.Methods  This study describes a small sample of patients who were diagnosed with HD during their hospital admission and not before. The discussion is whether the typical early signs and symptoms of HD are just not recognized, or whether unusual presentations confuse the attending physician.Results  A total of 23 HD patients were hospitalized during the study period, of which 6 (26%) were only diagnosed with HD during their admission. All were classified as lepromatous leprosy (LL) with a history of signs and symptoms of HD. In nearly all patients, a suspicion of HD might have been raised earlier if a careful history and dermato‐neurological examination had been done.Conclusions  Multibacillary (MB) HD, especially close to the lepromatous end of the spectrum, may mimic other diseases, and the patient can not be diagnosed without a biopsy or a slit skin smear examination. Clinicians working in a HD endemic area (Rio de Janeiro) do not always include HD in their differential diagnosis, especially when the clinical presentation is unusual. HD should be considered in all patients with skin lesions not responding to treatment, especially when they have neurological deficits, and live or have lived in an HD endemic area. Due to the increase in global travel and immigration, doctors in low endemic areas need to consider HD as a possible diagnosis.Conflicts of interestNone declared
Haemodynamic and respiratory effects of an abdominal compression binder
Authors: Toft Mette Helene , Bülow Jens , Simonsen Lene 
Published: September 2008

SummaryIn order to elucidate the circulatory and respiratory effects of a newly developed abdominal compression binder 25 healthy, normal weight subjects were studied. In supine position the central haemodynamics were measured and estimated with a Finapress device. Lower extremity venous haemodynamics were measured in supine position with venous occlusion plethysmography. In an upright‐seated position arterial oxygen saturation was measured by a pulseoxymeter for 1 h before spirometry was performed with a turbine flow measurement device. All the tests were performed in a randomized order with or without the abdominal compression binder. The results show that the compression binder significantly increases the venous volume in the lower extremities as showed by a reduction in the venous capacitance in the lower extremities and a reduction in the stroke volume and cardiac output, while it does not influence the pulmonary volumes.It is concluded that the applied abdominal binder significantly affects peripheral and central haemodynamics. It should therefore be used with caution when in the supine position for longer periods, as the pooling of blood it induces in the lower extremities may have implications for the risk of deep venous thrombosis formation.
Foreign Banks in Poor Countries: Theory and Evidence
Authors: DETRAGIACHE ENRICA , TRESSEL THIERRY , GUPTA POONAM 
Published: September 2008

ABSTRACTWe study how foreign bank penetration affects financial sector development in poor countries. A theoretical model shows that when domestic banks are better than foreign banks at monitoring soft information customers, foreign bank entry may hurt these customers and worsen welfare. The model also predicts that credit to the private sector should be lower in countries with more foreign bank penetration, and that foreign banks should have a less risky loan portfolio. In the empirical section, we test these predictions for a sample of lower income countries and find support for the theoretical model.
Collective Risk Management in a Flight to Quality Episode
Authors: CABALLERO RICARDO J. , KRISHNAMURTHY ARVIND 
Published: September 2008

ABSTRACTSevere flight to quality episodes involve uncertainty about the environment, not only risk about asset payoffs. The uncertainty is triggered by unusual events and untested financial innovations that lead agents to question their worldview. We present a model of crises and central bank policy that incorporates Knightian uncertainty. The model explains crisis regularities such as market‐wide capital immobility, agents' disengagement from risk, and liquidity hoarding. We identify a social cost of these behaviors, and a benefit of a lender of last resort facility. The benefit is particularly high because public and private insurance are complements during uncertainty‐driven crises.
The Real Determinants of Asset Sales
Authors: YANG LIU 
Published: September 2008

ABSTRACTI develop a dynamic structural model in which a firm makes rational decisions to buy or sell assets in the presence of productivity shocks. By identifying equilibrium asset prices, the model also examines the aggregate asset sales activity over the business cycle. It shows that changes in productivity, rather than productivity levels, affect decisions: Firms with rising productivity buy assets and firms with falling productivity downsize (“rising buys falling”). As such, industries in which firms have less persistent and more volatile productivity experience greater asset reallocation. Using plant‐level data from Longitudinal Research Database (LRD), I find strong support for the model's predictions.
Developing Expert Medical Teams: Toward an Evidence‐based Approach
Authors: Fernandez Rosemarie , Vozenilek John A. , Hegarty Cullen B. , Motola Ivette , Reznek Martin , Phrampus Paul E. , Kozlowski Steve W.J. 
Published: September 2008

AbstractCurrent health care literature cites communication breakdown and teamwork failures as primary threats to patient safety. The unique, dynamic environment of the emergency department (ED) and the complexity of patient care necessitate the development of strong interdisciplinary team skills among emergency personnel. As part of the 2008 Academic Emergency Medicine Consensus Conference on “The Science of Simulation in Healthcare,” our workshop group identified key theory and evidence‐based recommendations for the design and implementation of team training programs. The authors then conducted an extensive review of the team training literature within the domains of organizational psychology, aviation, military, management, and health care. This review, in combination with the workshop session, formed the basis for recommendations and need for further research in six key areas: 1) developing and refining core competencies for emergency medicine (EM) teams; 2) leadership training for emergency physicians (EPs); 3) conducting comprehensive needs analyses at the organizational, personnel, and task levels; 4) development of training platforms to maximize knowledge transfer; 5) debriefing and provision of feedback; and 6) proper implementation of simulation technology. The authors believe that these six areas should form an EM team training research platform to advance the EM literature, while leveraging the unique team structures present in EM to expand team training theory and research.
Effects of Computerized Provider Order Entry and Nursing Documentation on Workflow
Authors: Asaro Phillip V. , Boxerman Stuart B. 
Published: September 2008

AbstractObjectives:  The objective was to measure the effects of the implementation of computerized provider order entry (CPOE) and electronic nursing documentation on provider workflow in the emergency department (ED).Methods:  The authors performed a before‐and‐after time‐motion study of the activities of physicians and nurses. The percentages of time spent in task categories were calculated by provider session and averaged across provider sessions.Results:  There was a shift in physician time from working with paper alone, 13.1% to 9.6% (p = 0.05), to working with paper while using a computer, 1.6% to 4.3% (p = 0.02), and an increase in time spent working on computer and/or paper from 30.0% to 38.9% (p = 0.02). For nurses, the increase in time spent on computer from 9.5% to 25.7% (p < 0.01) was offset by a decrease in time spent working with paper from 16.5% to 1.8% (p < 0.01). Direct care decreased minimally for nurses from 56.9% to 55.3% (p = 0.69), but from 36.8% to 29.1% (p = 0.07) for physicians, approaching statistical significance. Care planning decreased for nurses from 9.4% to 6.4% (p = 0.04) and from 21.7% to 19.5% (p = 0.60) for physicians.Conclusions:  The net effects of an implementation on provider workflow depend not only on changes in tasks directly related to the provider–computer interface, but also on changes in underlying patient care processes and information flows. The authors observed an unanticipated shift in physician time from interacting with nurses and patients toward retrieving information from the electronic patient record. Implementers should carefully consider how implementations will affect information flow and then expect the unexpected.
Effects of a Triage Process Conversion on the Triage of High‐risk Presentations
Authors: Asaro Phillip V. , Lewis Lawrence M. 
Published: September 2008

AbstractObjectives:  The objective was to determine effects of a modification in triage process on triage acuity distribution in general and among patients with conditions requiring time‐sensitive therapy.Methods:  The authors retrospectively reviewed triage acuity distributions before and after modification of their triage process that entailed conversion from the Canadian Triage and Acuity Scale (CTAS) to the Emergency Severity Index (ESI). The authors calculated the ratio of the odds of being triaged to a nonemergent level (3, 4, or 5) under ESI to the odds of being triaged as nonemergent under CTAS. The authors calculated sensitivity and specificity of triage to an emergent acuity level (1 or 2) for identifying patients with common presentations who required time‐sensitive care.Results:  There were shifts from higher to lower acuity levels for all subsets, with odds ratios ranging from 2.80 (95% confidence interval [CI] = 2.75 to 2.86) for all patients to 21.39 (95% CI = 14.66 to 31.21) for patients over 55 years of age with a chief complaint of chest pain. The sensitivity of triage for identifying abdominal pain patients requiring admission to an intensive care unit (ICU) or operating room (OR) or emergency department (ED) death was 80.7% (95% CI = 73.2 to 86.5) before versus 50.8% (95% CI = 43.5 to 58.1) following the transition to ESI. Specificity under CTAS, 55.2% (95% CI = 54.0 to 56.4), was significantly lower than under ESI, 83.6% (95% CI = 82.7 to 84.4). The authors found similar effects for patients presenting with chest pain.Conclusions:  Monitoring for changes in the sensitivity of the triage process for detecting patients with potentially time‐sensitive conditions should be considered when modifying triage processes. Further work should be done to determine if the decreased sensitivity seen in this study occurs in other institutions converting to ESI, and potential causative factors should be explored.
The Proinflammatory Cytokine Response following Resuscitation in the Swine Model Depends on the Method of Ventricular Fibrillation Induction
Authors: Niemann James T. , Rosborough John , Youngquist Scott , Lewis Roger J. , Phan Quynh T. , Filler Scott 
Published: September 2008

AbstractObjectives:  A systemic inflammatory response has been reported following resuscitation from cardiac arrest. The purpose of this study was to compare the magnitude of the tumor necrosis factor‐α (TNF‐α) response in two different swine models of ventricular fibrillation (VF) arrest.Methods:  This was a randomized comparative trial conducted with domestic swine (N = 28, mean weight 40 kg, range 34–49 kg) of both genders. Anesthetized and instrumented swine were randomized to electrically induced VF (n = 14) or spontaneous VF induced by occlusion of a coronary artery (n = 14). After 8 minutes of VF, countershocks were given and standard advanced cardiac life support was initiated. Resuscitated animals were observed for 3 hours, and hemodynamics, base excess, and TNF‐α concentrations were measured at intervals.Results:  TNF‐α concentrations were significantly greater in the ischemic VF group throughout the postresuscitation period. Multivariate modeling demonstrated that the TNF‐α level was dependent on the method of VF induction and correlated with ischemia time (untreated VF period plus time to restoration of circulation) and the degree of postresuscitation hypoperfusion as reflected in base excess measurements.Conclusions:  This study demonstrates that TNF‐α concentrations increase after resuscitation from cardiac arrest and that the TNF‐α response is more profound in animals subjected to ischemic, spontaneous VF. The observed differences may be due to a longer resuscitation time and persistent postresuscitation hypoperfusion in the ischemic VF group. These differences need to be considered in studies evaluating mechanisms of postresuscitation organ dysfunction and defining mortality markers.
The Profitability of Medicare Admissions Based on Source of Admission
Authors: McHugh Megan , Regenstein Marsha , Siegel Bruce 
Published: September 2008

AbstractObjectives:  This study investigates whether admissions from the emergency department (ED) have lower dollar margins than elective admissions under Medicare and explores two possible reasons for differences in margins.Methods:  The authors developed patient‐level Medicare dollar margins (calculated as patient revenue minus cost) for 1,159,243 Medicare admissions from 321 hospitals using data from the 2003 Nationwide Inpatient Sample (NIS) and the Medicare Impact File. Differences in margins between ED and elective admissions were explored across a number of diagnosis‐related groups (DRGs) using t‐tests. Chi‐square tests were used explore whether ED admission was more common among patients in low‐profit DRGs and/or patients with greater severity of illness.Results:  The average Medicare dollar margins were −$712 (95% confidence interval [CI] = −$729 to −$695) for ED admissions and $22 (95% CI = −$2 to $47) for elective admissions. Medicare dollar margins for ED admissions were lower than those of elective admission for the most common DRGs. ED admission was associated with greater patient severity of illness.Conclusions:  Source of admission is a financially meaningful classification. Because Medicare payment policy does not recognize differences in cost based on patients’ route of admission, hospitals may have a financial incentive to favor elective admissions over ED admissions.