bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk of bias in industry-funded oseltamivir trials: comparison of core reports versus full clinical study reports
Authors: Jefferson Tom , Jones Mark A , Doshi Peter , Del Mar Chris B , Hama Rokuro , Thompson Matthew J , Onakpoya Igho , Heneghan Carl J
Published: October 2014

Background

The Cochrane risk of bias tool is a prominent instrument used to evaluate potential biases in clinical trials. In three updates of our Cochrane review on neuraminidase inhibitors, we assessed risk of bias on the same trials using different levels of detail: the trials in journal publications, in core reports, and in full clinical study reports. Here we analyse whether progressively greater amounts of information and detail in full clinical study reports (including trial protocols, statistical analysis plans, certificates of analyses, individual participant data listings and randomisation lists) affected our risk of bias assessments.

Methods and findings

We used the Cochrane risk of bias tool to assess and compare risk of bias in 14 oseltamivir trials (reported in 10 clinical study reports) obtained from the European Medicines Agency (EMA) and the manufacturer, Roche. With more detailed information, reported in clinical study reports, no previous assessment of ‘high’ risk of bias was reclassified as ‘low’ or ‘unclear’ in the main analysis, and over half (55%, 34/62) of the previous assessments of ‘low’ risk of bias were reclassified as ‘high’. Most assessments of ‘unclear’ risk of bias (67%, or 28/42) were reclassified as ‘high’ risk of bias when our judgements were based on full clinical study reports. The limits of our study were our relative inexperience in dealing with large information sets, sometimes subjective bias judgements and focus on industry trials. Comparison with journal publications was not possible because of the low number of trials published.

Conclusions

We found that as information increased in the document, this increased our assessment of bias. This may mean that risk of bias has been insufficiently assessed in Cochrane reviews based on journal publications.
Does a ‘direct’ transfer protocol reduce time to coronary angiography for patients with non-ST-elevation acute coronary syndromes? A prospective observational study
Authors: Gallagher S M , Lovell M J , Jones D A , Ferguson E , Ahktar A , Buckhoree Z , Wragg A , Knight C J , Mathur A , Smith E J , Cliffe S , Archbold R A , Rothman M T , Jain A K
Published: October 2014

Objective

National guidelines recommend ‘early’ coronary angiography within 96 h of presentation for patients with non-ST elevation acute coronary syndromes (NSTE-ACS). Most patients with NSTE-ACS present to their district general hospital (DGH), and await transfer to the regional cardiac centre for angiography. This care model has inherent time delays, and delivery of timely angiography is problematic. The objective of this study was to assess a novel clinical care pathway for the management of NSTE-ACS, known locally as the Heart Attack Centre-Extension or HAC-X, designed to rapidly identify patients with NSTE-ACS while in DGH emergency departments (ED) and facilitate transfer to the regional interventional centre for ‘early’ coronary angiography.

Methods

This was an observational study of 702 patients divided into two groups; 391 patients treated before the instigation of the HAC-X pathway (Pre-HAC-X), and 311 patients treated via the novel pathway (Post-HAC-X). Our primary study end point was time from ED admission to coronary angiography. We also assessed the length of hospital stay.

Results

Median time from ED admission to coronary angiography was 7.2 (IQR 5.1–10.2) days pre-HAC-X compared to 1.0 (IQR 0.7–2.0) day post-HAC-X (p<0.001). Median length of hospital stay was 3.0 (IQR 2.0–6.0) days post-HAC-X v 9.0 (IQR 6.0–14.0) days pre-HAC-X (p<0.0005). This equates to a reduction of six hospital bed days per NSTE-ACS admission.

Conclusions

The introduction of this novel care pathway was associated with significant reductions in time to angiography and in total hospital bed occupancy for patients with NSTE-ACS.
Beyond the ‘dyad’: a qualitative re-evaluation of the changing clinical consultation
Authors: Swinglehurst Deborah , Roberts Celia , Li Shuangyu , Weber Orest , Singy Pascal
Published: October 2014

Objective

To identify characteristics of consultations that do not conform to the traditionally understood communication ‘dyad’, in order to highlight implications for medical education and develop a reflective ‘toolkit’ for use by medical practitioners and educators in the analysis of consultations.

Design

A series of interdisciplinary research workshops spanning 12 months explored the social impact of globalisation and computerisation on the clinical consultation, focusing specifically on contemporary challenges to the clinician–patient dyad. Researchers presented detailed case studies of consultations, taken from their recent research projects. Drawing on concepts from applied sociolinguistics, further analysis of selected case studies prompted the identification of key emergent themes.

Setting

University departments in the UK and Switzerland.

Participants

Six researchers with backgrounds in medicine, applied linguistics, sociolinguistics and medical education. One workshop was also attended by PhD students conducting research on healthcare interactions.

Results

The contemporary consultation is characterised by a multiplicity of voices. Incorporation of additional voices in the consultation creates new forms of order (anddisorder) in the interaction. The roles ‘clinician’ and ‘patient’ are blurred as they become increasingly distributed between different participants. These new consultation arrangements make new demands on clinicians, which lie beyond the scope of most educational programmes for clinical communication.

Conclusions

The consultation is changing. Traditional consultation models that assume a ‘dyadic’ consultation do not adequately incorporate the realities of many contemporary consultations. A paradox emerges between the need to manage consultations in a ‘super-diverse’ multilingual society, while also attending to increasing requirements for standardised protocol-driven approaches to care prompted by computer use. The tension between standardisation and flexibility requires addressing in educational contexts. Drawing on concepts from applied sociolinguistics and the findings of these research observations, the authors offer a reflective ‘toolkit’ of questions to ask of the consultation in the context of enquiry-based learning.
The role and significance of nurses in managing transitions to palliative care: a qualitative study
Authors: Kirby Emma , Broom Alex , Good Phillip
Published: October 2014

Objectives

Nurses are generally present, and often influential, in supporting patient and family acceptance of medical futility and in assisting doctors in negotiating referral to palliative care. Yet the specificities of the nursing role and how nurses may contribute to timely and effective referrals is not well understood. This study aimed to systematically explore hospital-based nurses’ accounts of the transition to palliative care, and the potential role of nurses in facilitating more effective palliative care transitions.

Design

Qualitative study using semistructured interviews.

Setting

Two health services with public as well as private clinical environments in a major metropolitan area of Australia.

Participants

Hospital-based nurses (n=20) who regularly work with patients at the point of referral and in managing transitions to palliative care.

Results

Four significant themes emerged from thematic analysis. These include: (1) professional dynamics and the roles played by nurses in initiating the transition to palliative care; (2) the value of nurses’ informal interactions in timely and effective transitions; (3) the emerging challenge of managing task-oriented nursing versus intense emotional nursing work at the point of medical futility and (4) the emotional burden experienced by nurses within this clinical context. Nurses self-reported occupying critical albeit complex roles in the management of medical futility and the transition to palliative care. They reported experiencing significant emotional burden in balancing interpersonal and interprofessional relationships during this time.

Conclusions

The results suggest that nurses may be utilised in a more formalised and systematic fashion in the context of managing medical futility and the need to topicalise the transition, with the focus shifted away from medical referrals towards more team-based and patient-centred timely transitions. Further research focused on the experiences of doctors, allied health professionals, patients and families is required to provide a broader interdisciplinary understanding of futility and contributions to the negotiation of palliative care.
Changes in left ventricular relaxation after azelnidipine treatment in hypertensive patients with diabetes: subanalysis of a prospective single-arm multicentre study
Authors: Iwakura Katsuomi , Ito Hiroshi , Ishii Katsuhisa , Date Motoo , Nakamura Fumiaki , Nagano Toshihiko , Takiuchi Shin
Published: October 2014

Objectives

We previously demonstrated that a calcium channel blocker, azelnidipine, improves left ventricular relaxation in patients with hypertension and diastolic dysfunction in a multicentre, Clinical impact of Azelnidipine on Left VentricuLar diastolic function and OutComes in patients with hypertension (CALVLOC) trial. The objectives of the present subanalysis were to investigate the differences in diastolic function in hypertensive patients with and without diabetes, and the efficacy of azelnidipine on diastolic function among them.

Design

Subanalysis of a prospective single-arm multicentre study.

Participants

228 hypertensive patients with normal ejection fraction and impaired left ventricular relaxation (septal e′velocity <8 cm/s on echocardiography) enrolled for CALVLOC trial. They were divided into two groups based on presence or absence of diabetes.

Interventions

Administration of 16 mg of azelnidipine for 8 months (range 6–10 months).

Main outcome measures

Septal e′velocity before and at the end of the study.

Results

Whereas patients with diabetes (n=53, 23.2%) had lower systolic blood pressure (BP) than patients without diabetes (155±17 vs 161±16 mm Hg, p=0.03), they had lower e′velocity (5.7±1.5 vs 6.1±1.4 cm/s, p=0.04) at baseline. Azelnidipine decreased BP and heart rate, and increased e′velocity similarly in patients with diabetes (5.7±1.5 to 6.3±1.5 cm/s, p=0.0003) and without diabetes (6.1±1.4 to 6.9±1.4 cm/s, p<0.0001). Increase in e′velocity was not influenced by presence of diabetes, and patients with diabetes still had lower e′velocity after treatment (p=0.006). There was a significant correlation between increase in e′velocity and decrease in systolic BP (R=0.25, p=0.0001), which was not influenced by diabetes.

Conclusions

Comorbid diabetes could impair left ventricular relaxation independently in patients with hypertension, which might not be improved solely by BP lowering.
Associations of chronic individual-level and neighbourhood-level stressors with incident coronary heart disease: the Multi-Ethnic Study of Atherosclerosis
Authors: Kershaw Kiarri N , Diez Roux Ana V , Bertoni Alain , Carnethon Mercedes R , Everson-Rose Susan A , Liu Kiang
Published: October 2014

Background

Several individual-level stressors have been linked to incident coronary heart disease (CHD), but less attention has focused on the influence of neighbourhood-level sources of stress. In this study we examined prospective associations of individual-level and neighbourhood-level stressors with incident CHD.

Methods

Multi-Ethnic Study of Atherosclerosis participants aged 45–84 years at baseline (2000–2002) with complete data were included in the analyses (n=6678 for individual-level and n=6105 for neighbourhood-level stressors). CHD was defined as non-fatal myocardial infarction, resuscitated cardiac arrest or CHD death. Median follow-up was 10.2 years. Multivariable Cox proportional hazards models were fitted to estimate associations of individual-level and neighbourhood-level stressors (categorised into approximate tertiles) with incident CHD.

Results

Higher reported individual-level stressors were associated with higher incident CHD. Participants in the high individual-level stressor category had 65% higher risk of incident CHD (95% CI 1.23 to 2.22) than those in the low category after adjusting for sociodemographics (P for trend=0.002). This association weakened but remained significant with further adjustment for behavioural and biological risk factors. There was a non-linear relationship between neighbourhood-level stressors and incident CHD (P for quadratic term=0.01). Participants in the medium category had 49% higher CHD risk (95% CI 1.06 to 2.10) compared with those in the low category; those in the high category had only 27% higher CHD risk (95% CI 0.83 to 1.95). These associations persisted with adjustment for risk factors and individual-level stressors.

Conclusions

Individual-level and neighbourhood-level stressors were independently associated with incident CHD, though the nature of the relationships differed.
Creation of electron–positron pairs at excited Landau levels by neutrino in a strong magnetic field
Authors: Kuznetsov A. V. , Rumyantsev D. A. , Savin V. N.
Published: October 2014

The process of neutrino production of electron–positron pairs in a magnetic field of arbitrary strength, where electrons and positrons can be created in the states corresponding to excited Landau levels, is analyzed. The mean value of the neutrino energy loss due to the process ν → νe-e+ is calculated. The result can be applied for calculating the efficiency of the electron–positron plasma production by neutrinos in the conditions of the Kerr black hole accretion disk considered by experts as the most possible source of a short cosmological gamma burst. The presented research can also be useful for further development of the calculation technique for an analysis of quantum processes in external active medium, and in part in the conditions of moderately strong magnetic field, when taking account of the ground Landau level appears to be insufficient.
The flavor universality of some mass splittings in hadrons
Authors: Afonin S. S.
Published: October 2014

The approximate chiral invariance of the two-flavor (QCD) is known to be spontaneously broken. This effect explains the relatively small pion mass and, as is widely believed, the mass splittings of would-be chiral partners — the hadrons of equal spin but opposite parity lying in one multiplet of the chiral symmetry. We present experimental evidences that in reality such mass splittings in the meson sector seem to be approximately flavor-independent in all cases where they can be tested experimentally — the spin 0 and 1. In addition, a partial flavor independence holds for spin-1/2 baryons (namely among states in which at least one of the quark is not u or d one). This property allow to predict masses and quantum numbers for 10 new hadrons. The given flavor-independence, if confirmed for higher spins, hints at the existence of universal scale Λ strong ~300 MeV in the strong interactions which, in contrast to Λ QCD , is flavor and scheme independent. Some manifestations of Λ strong are discussed.
THE BINOMIAL INTERPOLATED LATTICE METHOD FOR STEP DOUBLE BARRIER OPTIONS
Authors: APPOLLONI ELISA , GAUDENZI MARCELLINO , ZANETTE ANTONINO
Published: October 2014

We consider the problem of pricing step double barrier options with binomial lattice methods. We introduce an algorithm, based on interpolation techniques, that is robust and efficient, that treats the "near barrier" problem for double barrier options and permits the valuation of step double barrier options with American features. We provide a complete convergence analysis of the proposed lattice algorithm in the European case.
CALIBRATION OF THE UNI-VARIATE COX–INGERSOLL–ROSS MODEL AND PARAMETERS SELECTION THROUGH THE KULLBACK–LEIBLER DIVERGENCE
Authors: DANG-NGUYEN STEPHANE , LE CAILLEC JEAN-MARC , HILLION ALAIN
Published: October 2014

This paper proposes a new estimation algorithm for the uni-variate Cox–Ingersoll–Ross (CIR) model in the state-space framework. The selection criterion among parameters is the likelihood but some parameters may have the same value; thus the initialization of the optimization routine is important especially if deterministic solvers are used. The algorithm aims at combining likelihood and two additional criteria based on the Kullback–Leibler divergence in order to find initial values in a grid search. The likelihood is then optimized in a restricted parameter set. A numerical experiment consists of generating data given a parameter set varying the length of the time series and the observation noise and then estimating the parameters with the algorithm. The results are discussed showing different performance levels for each parameter.
JUSTIFICATION OF PER-UNIT RISK CAPITAL ALLOCATION IN PORTFOLIO CREDIT RISK MODELS
Authors: DORFLEITNER GREGOR , PFISTER TAMARA
Published: October 2014

Risk capital allocation is based on the assumption that the risk of a homogeneous portfolio is scaled up and down with the portfolio size. In this article we show that this assumption is true for large portfolios, but has to be revised for small ones. On basis of numerical examples we calculate the minimum portfolio size that is necessary to limit the error of gradient risk capital allocation and the resulting error in a portfolio optimization algorithm or pricing strategy. We show the dependency of this minimum portfolio size on different parameters like the probability of default and on the credit risk model that is used.
OPTIMALITY OF PAYOFFS IN LÉVY MODELS
Authors: VON HAMMERSTEIN ERNST AUGUST , LÜTKEBOHMERT EVA , RÜSCHENDORF LUDGER , WOLF VIKTOR
Published: October 2014

In this paper, we determine the lowest cost strategy for a given payoff in Lévy markets where the pricing is based on the Esscher martingale measure. In particular, we consider Lévy models where prices are driven by a normal inverse Gaussian (NIG)- or a variance Gamma (VG)-process. Explicit solutions for cost-efficient strategies are derived for a variety of vanilla options, spreads, and forwards. Applications to real financial market data show that the cost savings associated with these strategies can be quite substantial. The empirical findings are supplemented by a result that relates the magnitude of these savings to the strength of the market trend. Moreover, we consider the problem of hedging efficient claims, derive explicit formulas for the deltas of efficient calls and puts and apply the results to German stock market data. Using the time-varying payoff profile of efficient options, we further develop alternative delta hedging strategies for vanilla calls and puts. We find that the latter can provide a more accurate way of replicating the final payoff compared to their classical counterparts.
A Mixed 4-Node 3D Plate Element Based on Self-Equilibrated Isostatic Stresses
Authors: Madeo Antonio , Zagari Giuseppe , Casciaro Raffaele , de Miranda Stefano
Published: October 2014

A new mixed stress 4-node flat shell finite element, designed for the linear and nonlinear analysis of folded plate structures, is presented. The kinematics of the element is defined by 24 dofs with in- and out-of-plane displacements assumed to be quadratic, controlled by displacement and rotation parameters through an Allman like interpolation, and flexural rotations assumed to be bilinear. The assumed stress approximation, described within a local Cartesian frame aligned with the element orientation, is self-equilibrated and ruled by the minimum number of parameters. The element does not suffer from kinematical locking and rank defectiveness. Many numerical tests show the very good performance of the element.
A Novel CEEMD-Based EELM Ensemble Learning Paradigm for Crude Oil Price Forecasting
Authors: Tang Ling , Dai Wei , Yu Lean , Wang Shouyang
Published: October 2014

To enhance the prediction accuracy for crude oil price, a novel ensemble learning paradigm coupling complementary ensemble empirical mode decomposition (CEEMD) and extended extreme learning machine (EELM) is proposed. This novel method is actually an improved model under the effective "decomposition and ensemble" framework, especially for nonlinear, complex, and irregular data. In this proposed method, CEEMD, a current extension from the competitive decomposition family of empirical mode decomposition (EMD), is first applied to divide the original data (i.e., difficult task) into a number of components (i.e., relatively easy subtasks). Then, EELM, a recently developed, powerful, fast and stable intelligent learning technique, is implemented to predict all extracted components individually. Finally, these predicted results are aggregated into an ensemble result as the final prediction using simple addition ensemble method. With the crude oil spot prices of WTI and Brent as sample data, the empirical results demonstrate that the novel CEEMD-based EELM ensemble model statistically outperforms all listed benchmarks (including typical forecasting techniques and similar ensemble models with other decomposition and ensemble tools) in prediction accuracy. The results also indicate that the novel model can be used as a promising forecasting tool for complicated time series data with high volatility and irregularity.
Families of weighted sum formulas for multiple zeta values
Authors: Guo Li , Lei Peng , Zhao Jianqiang
Published: October 2014

Euler's sum formula and its multi-variable and weighted generalizations form a large class of the identities of multiple zeta values. In this paper, we prove a family of identities involving Bernoulli numbers and apply them to obtain infinitely many weighted sum formulas for double zeta values and triple zeta values where the weight coefficients are given by symmetric polynomials. We give a general conjecture in arbitrary depth at the end of the paper.
Electrical properties modulation of thin film solar cell using gold nanostructures at textured FTO/p–i–n interface
Authors: Gentile A. , Cacciato G. , Ruffino F. , Reitano R. , Scapellato G. , Zimbone M. , Grimaldi M. G. , Lombardo S. , Battaglia A. , Gerardi C. , Foti M.
Published: October 2014

We report about the modulation of the electrical properties of thin film solar cells due to the incorporation of size-selected Au nanostructures (NSs) at a textured FTO/p–i–n interface. By increasing the Au NSs size, the analyses of current-voltage characteristics show lower Schottky barrier heights and the gradual reduction of the open-circuit voltages (V OC ). The optical measurements show higher parasitic absorption by larger Au NSs that reduces the amount of radiation transmitted by the transparent to absorber layer. This process decreases the number of photo-generated carriers and may explain the V OC reduction related to the devices with larger Au NSs at the interface. So, the correlation between materials properties and device performances was established.
On the symmetric digraphs from the kth power mapping on finite commutative rings
Authors: Deng Guixin , Somer Lawrence
Published: October 2014

For a finite commutative ring R and a positive integer k, let G(R, k) denote the digraph whose set of vertices is R and for which there is a directed edge from a to ak. The digraph G(R, k) is called symmetric of order M if its set of connected components can be partitioned into subsets of size M with each subset containing M isomorphic components. We primarily aim to factor G(R, k) into the product of its subdigraphs. If the characteristic of R is a prime p, we obtain several sufficient conditions for G(R, k) to be symmetric of order M.
NONLINEAR SPIN WAVES IN GRAPHENE STRUCTURES
Authors: GRACHEV D. D. , SEVASTYANOV L. A. , LOVETSKIY K. P. , GUSEV A. A. , VINITSKY S. I. , DERBOV V. L.
Published: October 2014

Basing on Dirac equation for interacting massless fermions, we propose a nonlinear model that describes a possible mechanism of ferromagnetism in graphene structures, resulting from electron–electron interaction and spontaneous breaking of spin symmetry of valence electrons. Qualitative predictions of the model are important for practical applications in spintronics. Localized kink–antikink patterns of valence electron spin density on the graphene surface are calculated, their interaction is described, and, finally, the formation of their quasi-bound metastable states (breathers) is investigated. The spectrum of breathers is calculated in both the analytical and the numerical form. Possible inverted population of the appropriate states may be used to generate quantum coherent nonlinear spin waves that can find practical applications in nanoelectronics and spintronics.
Dynamic and Robust Local Clearance Triangulations
Authors: Kallmann Marcelo
Published: October 2014

The Local Clearance Triangulation (LCT) of polygonal obstacles is a cell decomposition designed for the efficient computation of locally shortest paths with clearance. This article presents a revised definition of LCTs, new theoretical results and optimizations, and new algorithms introducing dynamic updates and robustness. Given an input obstacle set with
n
vertices, a theoretical analysis is proposed showing that LCTs generate a triangular decomposition of
O
(
n
) cells, guaranteeing that discrete search algorithms can compute paths in optimal times. In addition, several examples are presented indicating that the number of triangles is low in practice, close to 2
n
, and a new technique is described for reducing the number of triangles when the maximum query clearance is known in advance. Algorithms for repairing the local clearance property dynamically are also introduced, leading to efficient LCT updates for addressing dynamic changes in the obstacle set. Dynamic updates automatically handle intersecting and overlapping segments with guaranteed robustness, using techniques that combine one exact geometric predicate with adjustment of illegal floating-point coordinates. The presented results demonstrate that LCTs are efficient and highly flexible for representing dynamic polygonal environments with clearance information.
A Framework for Hierarchical Ensemble Clustering
Authors: Zheng Li , Li Tao , Ding Chris
Published: October 2014

Ensemble clustering, as an important extension of the clustering problem, refers to the problem of combining different (input) clusterings of a given dataset to generate a final (consensus) clustering that is a better fit in some sense than existing clusterings. Over the past few years, many ensemble clustering approaches have been developed. However, most of them are designed for partitional clustering methods, and few research efforts have been reported for ensemble hierarchical clustering methods. In this article, a hierarchical ensemble clustering framework that can naturally combine both partitional clustering and hierarchical clustering results is proposed. In addition, a novel method for learning the ultra-metric distance from the aggregated distance matrices and generating final hierarchical clustering with enhanced cluster separation is developed based on the ultra-metric distance for hierarchical clustering. We study three important problems: dendrogram description, dendrogram combination, and dendrogram selection. We develop two approaches for dendrogram selection based on tree distances, and we investigate various dendrogram distances for representing dendrograms. We provide a systematic empirical study of the ensemble hierarchical clustering problem. Experimental results demonstrate the effectiveness of our proposed approaches.
Automating Image Morphing Using Structural Similarity on a Halfway Domain
Authors: Liao Jing , Lima Rodolfo S. , Nehab Diego , Hoppe Hugues , Sander Pedro V. , Yu Jinhui
Published: October 2014

The main challenge in achieving good image morphs is to create a map that aligns corresponding image elements. Our aim is to help automate this often tedious task. We compute the map by optimizing the compatibility of corresponding warped image neighborhoods using an adaptation of structural similarity. The optimization is regularized by a thin-plate spline and may be guided by a few user-drawn points. We parameterize the map over a halfway domain and show that this representation offers many benefits. The map is able to treat the image pair symmetrically, model simple occlusions continuously, span partially overlapping images, and define extrapolated correspondences. Moreover, it enables direct evaluation of the morph in a pixel shader without mesh rasterization. We improve the morphs by optimizing quadratic motion paths and by seamlessly extending content beyond the image boundaries. We parallelize the algorithm on a GPU to achieve a responsive interface and demonstrate challenging morphs obtained with little effort.
Real-Time Continuous Pose Recovery of Human Hands Using Convolutional Networks
Authors: Tompson Jonathan , Stein Murphy , Lecun Yann , Perlin Ken
Published: October 2014

We present a novel method for real-time continuous pose recovery of markerless complex articulable objects from a single depth image. Our method consists of the following stages: a randomized decision forest classifier for image segmentation, a robust method for labeled dataset generation, a convolutional network for dense feature extraction, and finally an inverse kinematics stage for stable real-time pose recovery. As one possible application of this pipeline, we show state-of-the-art results for real-time puppeteering of a skinned hand-model.
Procedural Design of Exterior Lighting for Buildings with Complex Constraints
Authors: Schwarz Michael , Wonka Peter
Published: October 2014

We present a system for the lighting design of procedurally modeled buildings. The design is procedurally specified as part of the ordinary modeling workflow by defining goals for the illumination that should be attained and locations where luminaires may be installed to realize these goals. Additionally, constraints can be modeled that make the arrangement of the installed luminaires respect certain aesthetic and structural considerations. From this specification, the system automatically generates a lighting solution for any concrete model instance. The underlying, intricate joint optimization and constraint satisfaction problem is approached with a stochastic scheme that operates directly in the complex subspace where all constraints are observed. To navigate this subspace efficaciously, the actual lighting situation is taken into account. We demonstrate our system on multiple examples spanning a variety of architectural structures and lighting designs.
RayCore
Authors: Nah Jae-Ho , Kwon Hyuck-Joo , Kim Dong-Seok , Jeong Cheol-Ho , Park Jinhong , Han Tack-Don , Manocha Dinesh , Park Woo-Chan
Published: October 2014

We present RayCore, a mobile ray-tracing hardware architecture. RayCore facilitates high-quality rendering effects, such as reflection, refraction, and shadows, on mobile devices by performing real-time Whitted ray tracing. RayCore consists of two major components: ray-tracing units (RTUs) based on a unified traversal and intersection pipeline and a tree-building unit (TBU) for dynamic scenes. The overall RayCore architecture offers considerable benefits in terms of die area, memory access, and power consumption. We have evaluated our architecture based on FPGA and ASIC evaluations and demonstrate its performance on different benchmarks. According to the results, our architecture demonstrates high performance per unit area and unit energy, making it highly suitable for use in mobile devices.
Fast Local Laplacian Filters
Authors: Aubry Mathieu , Paris Sylvain , Hasinoff Samuel W. , Kautz Jan , Durand Frédo
Published: October 2014

Multiscale manipulations are central to image editing but also prone to halos. Achieving artifact-free results requires sophisticated edge-aware techniques and careful parameter tuning. These shortcomings were recently addressed by the local Laplacian filters, which can achieve a broad range of effects using standard Laplacian pyramids. However, these filters are slow to evaluate and their relationship to other approaches is unclear. In this article, we show that they are closely related to anisotropic diffusion and to bilateral filtering. Our study also leads to a variant of the bilateral filter that produces cleaner edges while retaining its speed. Building upon this result, we describe an acceleration scheme for local Laplacian filters on gray-scale images that yields speedups on the order of 50×. Finally, we demonstrate how to use local Laplacian filters to alter the distribution of gradients in an image. We illustrate this property with a robust algorithm for photographic style transfer.
Physics-Based Anomaly Detection Defined on Manifold Space
Authors: Huang Hao , Qin Hong , Yoo Shinjae , Yu Dantong
Published: October 2014

Current popular anomaly detection algorithms are capable of detecting global anomalies but often fail to distinguish local anomalies from normal instances. Inspired by contemporary physics theory (i.e., heat diffusion and quantum mechanics), we propose two unsupervised anomaly detection algorithms. Building on the embedding manifold derived from heat diffusion, we devise Local Anomaly Descriptor (LAD), which faithfully reveals the intrinsic neighborhood density. It uses a scale-dependent umbrella operator to bridge global and local properties, which makes LAD more informative within an adaptive scope of neighborhood. To offer more stability of local density measurement on scaling parameter tuning, we formulate Fermi Density Descriptor (FDD), which measures the probability of a fermion particle being at a specific location. By choosing the stable energy distribution function, FDD steadily distinguishes anomalies from normal instances with any scaling parameter setting. To further enhance the efficacy of our proposed algorithms, we explore the utility of anisotropic Gaussian kernel (AGK), which offers better manifold-aware affinity information. We also quantify and examine the effect of different Laplacian normalizations for anomaly detection. Comprehensive experiments on both synthetic and benchmark datasets verify that our proposed algorithms outperform the existing anomaly detection algorithms.
Multiple-Fluid SPH Simulation Using a Mixture Model
Authors: Ren Bo , Li Chenfeng , Yan Xiao , Lin Ming C. , Bonet Javier , Hu Shi-Min
Published: October 2014

This article presents a versatile and robust SPH simulation approach for multiple-fluid flows. The spatial distribution of different phases or components is modeled using the volume fraction representation, the dynamics of multiple-fluid flows is captured by using an improved mixture model, and a stable and accurate SPH formulation is rigorously derived to resolve the complex transport and transformation processes encountered in multiple-fluid flows. The new approach can capture a wide range of real-world multiple-fluid phenomena, including mixing/unmixing of miscible and immiscible fluids, diffusion effect and chemical reaction, etc. Moreover, the new multiple-fluid SPH scheme can be readily integrated into existing state-of-the-art SPH simulators, and the multiple-fluid simulation is easy to set up. Various examples are presented to demonstrate the effectiveness of our approach.
Abstractions for software-defined networks
Authors: Casado Martin , Foster Nate , Guha Arjun
Published: October 2014

New abstractions are critical for achieving SDN goals.
Dissection
Authors: Dinur Itai , Dunkelman Orr , Keller Nathan , Shamir Adi
Published: October 2014

Combinatorial search problems are usually described by a collection of possible states, a list of possible actions which map each current state into some next state, and a pair of initial and final states. The algorithmic problem is to find a sequence of actions which maps the given initial state into the desired final state. In this paper, we introduce the new notion of
bicomposite search problems
, and show that they can be solved with improved combinations of time and space complexities by using a new algorithmic paradigm called
dissection
. To demonstrate the broad applicability of our new paradigm, we show how to use it in order to untangle Rubik's cube and to solve a typical NP-complete partition problem with algorithms which are better than any previously described algorithm for these problems.
Real-time deep virtual machine introspection and its applications
Authors: Hizver Jennia , Chiueh Tzi-cker
Published: October 2014

Virtual Machine Introspection (VMI) provides the ability to monitor virtual machines (VM) in an agentless fashion by gathering VM execution states from the hypervisor and analyzing those states to extract information about a running operating system (OS) without installing an agent inside the VM. VMI's main challenge lies in the difficulty in converting low-level byte string values into high-level semantic states of the monitored VM's OS. In this work, we tackle this challenge by developing a real-time kernel data structure monitoring (RTKDSM) system that leverages the rich OS analysis capabilities of Volatility, an open source computer forensics framework, to significantly simplify and automate analysis of VM execution states. The RTKDSM system is designed as an extensible software framework that is meant to be extended to perform application-specific VM state analysis. In addition, the RTKDSM system is able to perform real-time monitoring of any changes made to the extracted OS states of guest VMs. This real-time monitoring capability is especially important for VMI-based security applications. To minimize the performance overhead associated with real-time kernel data structure monitoring, the RTKDSM system has incorporated several optimizations whose effectiveness is reported in this paper.
COMMA
Authors: Zheng Jie , Ng Tze Sing Eugene , Sripanidkulchai Kunwadee , Liu Zhaolei
Published: October 2014

Multi-tier applications are widely deployed in today's virtualized cloud computing environments. At the same time, management operations in these virtualized environments, such as load balancing, hardware maintenance, workload consolidation, etc., often make use of live virtual machine (VM) migration to control the placement of VMs. Although existing solutions are able to migrate a single VM efficiently, little attention has been devoted to migrating related VMs in multi-tier applications. Ignoring the relatedness of VMs during migration can lead to serious application performance degradation. This paper formulates the multi-tier application migration problem, and presents a new communication-impact-driven coordinated approach, as well as a system called COMMA that realizes this approach. Through extensive testbed experiments, numerical analyses, and a demonstration of COMMA on Amazon EC2, we show that this approach is highly effective in minimizing migration's impact on multi-tier applications' performance.
CMD
Authors: Chen Licheng , Wei Zhipeng , Cui Zehan , Chen Mingyu , Pan Haiyang , Bao Yungang
Published: October 2014

Limited main memory size is considered as one of the major bottlenecks in virtualization environments. Content-Based Page Sharing (CBPS) is an efficient memory deduplication technique to reduce server memory requirements, in which pages with same content are detected and shared into a single copy. As the widely used implementation of CBPS, Kernel Samepage Merging (KSM) maintains the whole memory pages into two global comparison trees (a stable tree and an unstable tree). To detect page sharing opportunities, each tracked page needs to be compared with pages already in these two large global trees. However since the vast majority of compared pages have different content with it, that will induce massive futility comparisons and thus heavy overhead.

In this paper, we propose a lightweight page Classification-based Memory Deduplication approach named CMD to reduce futile page comparison overhead meanwhile to detect page sharing opportunities efficiently. The main innovation of CMD is that pages are grouped into different classifications based on page access characteristics. Pages with similar access characteristics are suggested to have higher possibility with same content, thus they are grouped into the same classification. In CMD, the large global comparison trees are divided into multiple small trees with dedicated local ones in each page classification. Page comparisons are performed just in the same classification, and pages from different classifications are never compared (since they probably result in futile comparisons). The experimental results show that CMD can efficiently reduce page comparisons (by about 68.5%) meanwhile detect nearly the same (by more than 98%) or even more page sharing opportunities.
Friendly barriers
Authors: Kumar Vivek , Blackburn Stephen M. , Grove David
Published: October 2014

This paper addresses the problem of efficiently supporting parallelism within a managed runtime. A popular approach for exploiting software parallelism on parallel hardware is task parallelism, where the programmer explicitly identifies potential parallelism and the runtime then schedules the work. Work-stealing is a promising scheduling strategy that a runtime may use to keep otherwise idle hardware busy while relieving overloaded hardware of its burden. However, work-stealing comes with substantial overheads. Recent work identified sequential overheads of work-stealing, those that occur even when no stealing takes place, as a significant source of overhead. That work was able to reduce sequential overheads to just 15%.

In this work, we turn to dynamic overheads, those that occur each time a steal takes place. We show that the dynamic overhead is dominated by introspection of the victim's stack when a steal takes place. We exploit the idea of a low overhead return barrier to reduce the dynamic overhead by approximately half, resulting in total performance improvements of as much as 20%. Because, unlike prior work, we attack the overheads directly due to stealing and therefore attack the overheads that grow as parallelism grows, we improve the scalability of work-stealing applications. This result is complementary to recent work addressing the sequential overheads of work-stealing. This work therefore substantially relieves work-stealing of the increasing pressure due to increasing intra-node hardware parallelism.
A platform for secure static binary instrumentation
Authors: Zhang Mingwei , Qiao Rui , Hasabnis Niranjan , Sekar R.
Published: October 2014

Program instrumentation techniques form the basis of many recent software security defenses, including defenses against common exploits and security policy enforcement. As compared to source-code instrumentation, binary instrumentation is easier to use and more broadly applicable due to the ready availability of binary code. Two key features needed for security instrumentations are (a) it should be applied to all application code, including code contained in various system and application libraries, and (b) it should be non-bypassable. So far, dynamic binary instrumentation (DBI) techniques have provided these features, whereas static binary instrumentation (SBI) techniques have lacked them. These features, combined with ease of use, have made DBI the de facto choice for security instrumentations. However, DBI techniques can incur high overheads in several common usage scenarios, such as application startups, system-calls, and many real-world applications. We therefore develop a new platform for secure static binary instrumentation (PSI) that overcomes these drawbacks of DBI techniques, while retaining the security, robustness and ease-of-use features. We illustrate the versatility of PSI by developing several instrumentation applications: basic block counting, shadow stack defense against control-flow hijack and return-oriented programming attacks, and system call and library policy enforcement. While being competitive with the best DBI tools on CPU-intensive SPEC 2006 benchmark, PSI provides an order of magnitude reduction in overheads on a collection of real-world applications.
Deoptimization for dynamic language JITs on typed, stack-based virtual machines
Authors: Kedlaya Madhukar N. , Robatmili Behnam , Caşcaval Cġlin , Hardekopf Ben
Published: October 2014

We are interested in implementing dynamic language runtimes on top of language-level virtual machines. Type specialization is a critical optimization for dynamic language runtimes: generic code that handles any type of data is replaced with specialized code for particular types observed during execution. However, types can change, and the runtime must recover whenever unexpected types are encountered. The state-of-the-art recovery mechanism is called deoptimization. Deoptimization is a well-known technique for dynamic language runtimes implemented in low-level languages like C. However, no dynamic language runtime implemented on top of a virtual machine such as the Common Language Runtime (CLR) or the Java Virtual Machine (JVM) uses deoptimization, because the implementation thereof used in low-level languages is not possible.

In this paper we propose a novel technique that enables deoptimization for dynamic language runtimes implemented on top of typed, stack-based virtual machines. Our technique does not require any changes to the underlying virtual machine. We implement our proposed technique in a JavaScript language implementation, MCJS, running on top of the Mono runtime (CLR). We evaluate our implementation against the current state-of-the-art recovery mechanism for virtual machine-based runtimes, as implemented both in MCJS and in IronJS. We show that deoptimization provides significant performance benefits, even for runtimes running on top of a virtual machine.
MuscalietJS
Authors: Robatmili Behnam , Cascaval Calin , Reshadi Mehrdad , Kedlaya Madhukar N. , Fowler Seth , Bhavsar Vrajesh , Weber Michael , Hardekopf Ben
Published: October 2014

Layered JavaScript engines, in which the JavaScript runtime is built on top another managed runtime, provide better extensibility and portability compared to traditional monolithic engines. In this paper, we revisit the design of layered JavaScript engines and propose a layered architecture, called MuscalietJS2, that splits the responsibilities of a JavaScript engine between a high-level, JavaScript-specific component and a low-level, language-agnostic .NET VM. To make up for the performance loss due to layering, we propose a two pronged approach: high-level JavaScript optimizations and exploitation of low-level VM features that produce very efficient code for hot functions. We demonstrate the validity of the MuscalietJS design through a comprehensive evaluation using both the Sunspider benchmarks and a set of web workloads. We demonstrate that our approach outperforms other layered engines such as IronJS and Rhino engines while providing extensibility, adaptability and portability.
Experiences in the land of virtual abstractions
Authors: Hunt Galen C.
Published: October 2014

The Microsoft Research Drawbridge Project began with a simple question: Is it possible to achieve the benefits of hardware virtual machines without the overheads? Following that question, we have built a line of exploratory prototypes. These prototypes range from an ARM-based phone that runs x86 Windows binaries to new forms of secure computation. In this talk, I'll briefly describe our various prototypes and the evidence we have accumulated that our first question can be answered in the affirmative.