bluuebunny/crossref_metadata_2025 huggingface dataset:
TH‐CD‐207B‐05: Measurement of CT Bow‐Tie Profiles Using a Linear Array Detector
Authors: Yang K , Li X , Liu B
Published: July 2016

Purpose:

To accurately measure CT bow‐tie profiles from various manufacturers and to provide non‐proprietary information for CT system modeling.

Methods:

A GOS‐based linear detector (0.8 mm per pixel and 51.2 cm in length) with a fast data sampling speed (0.24 ms/sample) was used to measure the relative profiles of bow‐tie filters from a collection of eight CT scanners by three different vendors, GE (LS Xtra, LS VCT, Discovery HD750), Siemens (Sensation 64, Edge, Flash, Force), and Philips (iBrilliance 256). The linear detector was first calibrated for its energy response within typical CT beam quality ranges and compared with an ion chamber and analytical modeling (SPECTRA and TASMIP). A geometrical calibration process was developed to determine key parameters including the distance from the focal spot to the linear detector, the angular increment of the gantry at each data sampling, the location of the central x‐ray on the linear detector, and the angular response of the detector pixel. Measurements were performed under axial‐scan modes for most representative bow‐tie filters and kV selections from each scanner. Bow‐tie profiles were determined by re‐binning the measured rotational data with an angular accuracy of 0.1 degree using the calibrated geometrical parameters.

Results:

The linear detector demonstrated an energy response as a solid state detector, which is close to the CT imaging detector. The geometrical calibration was proven to be sufficiently accurate (< 1mm in error for distances >550 mm) and the bow‐tie profiles measured from rotational mode matched closely to those from the gantry‐stationary mode. Accurate profiles were determined for a total of 21 bow‐tie filters and 83 filter/kV combinations from the abovementioned scanner models.

Conclusion:

A new improved approach of CT bow‐tie measurement was proposed and accurate bow‐tie profiles were provided for a broad list of CT scanner models.
TH‐CD‐207B‐09: Task‐Driven Fluence Field Modulation Design for Model‐Based Iterative Reconstruction in CT
Authors: Gang G , Siewerdsen J , Stayman J
Published: July 2016

Purpose:

There has been increasing interest in integrating fluence field modulation (FFM) devices with diagnostic CT scanners for dose reduction purposes. Conventional FFM strategies, however, are often either based on heuristics or the analysis of filtered‐backprojection (FBP) performance. This work investigates a prospective task‐driven optimization of FFM for model‐based iterative reconstruction (MBIR) in order to improve imaging performance at the same total dose as conventional strategies.

Methods:

The task‐driven optimization framework utilizes an ultra‐low dose 3D scout as a patient‐specific anatomical model and a mathematical formation of the imaging task. The MBIR method investigated is quadratically penalized‐likelihood reconstruction. The FFM objective function uses detectability index, d’, computed as a function of the predicted spatial resolution and noise in the image. To optimize performance throughout the object, a maxi‐min objective was adopted where the minimum d’ over multiple locations is maximized. To reduce the dimensionality of the problem, FFM is parameterized as a linear combination of 2D Gaussian basis functions over horizontal detector pixels and projection angles. The coefficients of these bases are found using the covariance matrix adaptation evolution strategy (CMA‐ES) algorithm. The task‐driven design was compared with three other strategies proposed for FBP reconstruction for a calcification cluster discrimination task in an abdomen phantom.

Results:

The task‐driven optimization yielded FFM that was significantly different from those designed for FBP. Comparing all four strategies, the task‐based design achieved the highest minimum d’ with an 8–48% improvement, consistent with the maxi‐min objective. In addition, d’ was improved to a greater extent over a larger area within the entire phantom.

Conclusion:

Results from this investigation suggests the need to re‐evaluate conventional FFM strategies for MBIR. The task‐based optimization framework provides a promising approach that maximizes imaging performance under the same total dose constraint.
TH‐D‐BRB‐01: Scripting Fundamentals: Killing Cancer with Code
Authors: Popple R.
Published: July 2016

Scripting capabilities and application programming interfaces (APIs) are becoming commonly available in modern treatment planning systems. These links to the treatment planning system (TPS) allow users to read data from the TPS, and in some cases use TPS functionality and write data back to the TPS. Such tools are powerful extensions, allowing automation of routine clinical tasks and supporting research, particularly research involving repetitive tasks on large patient populations. The data and functionality exposed by scripting/API capabilities is vendor dependent, as are the languages used by script/API engines, such as the Microsoft .NET framework or Python. Scripts deployed in a clinical environment must be commissioned and validated like any other software tool. This session will provide an overview of scripting applications and a discussion of best practices, followed by a practical introduction to the scripting capabilities of three commercial treatment planning systems.

Learning Objectives:

Understand the scripting capabilities available in several treatment planning systems

Learn how to get started using scripting capabilities

Understand the best practices for safe script deployment in a clinical environment

R. Popple, Varian Medical Systems has provided research support unrelated to the topic of this session.R. Cardan, Varian Medical Systems for grant research, product evaluation, and teaching honorarium.
TH‐D‐BRB‐02: Eclipse Scripting Fundamentals in .NET
Authors: Cardan R.
Published: July 2016

Scripting capabilities and application programming interfaces (APIs) are becoming commonly available in modern treatment planning systems. These links to the treatment planning system (TPS) allow users to read data from the TPS, and in some cases use TPS functionality and write data back to the TPS. Such tools are powerful extensions, allowing automation of routine clinical tasks and supporting research, particularly research involving repetitive tasks on large patient populations. The data and functionality exposed by scripting/API capabilities is vendor dependent, as are the languages used by script/API engines, such as the Microsoft .NET framework or Python. Scripts deployed in a clinical environment must be commissioned and validated like any other software tool. This session will provide an overview of scripting applications and a discussion of best practices, followed by a practical introduction to the scripting capabilities of three commercial treatment planning systems.

Learning Objectives:

Understand the scripting capabilities available in several treatment planning systems

Learn how to get started using scripting capabilities

Understand the best practices for safe script deployment in a clinical environment

R. Popple, Varian Medical Systems has provided research support unrelated to the topic of this session.R. Cardan, Varian Medical Systems for grant research, product evaluation, and teaching honorarium.
TH‐E‐201‐00: Teaching Radiology Residents: What, How, and Expectation
Authors: Zhang Jie
Published: July 2016

The ABR Core Examination stresses integrating physics into real‐world clinical practice and, accordingly, has shifted its focus from passive recall of facts to active application of physics principles. Physics education of radiology residents poses a challenge. The traditional method of didactic lectures alone is insufficient, yet it is difficult to incorporate physics teaching consistently into clinical rotations due to time constraints.

Faced with this challenge, diagnostic medical physicists who teach radiology residents, have been thinking about how to adapt their teaching to the new paradigm, what to teach and meet expectation of the radiology resident and the radiology residency program. The proposed lecture attempts to discuss above questions. Newly developed diagnostic radiology residents physics curriculum by the AAPM Imaging Physics Curricula Subcommittee will be reviewed. Initial experience on hands‐on physics teaching will be discussed. Radiology resident who will have taken the BAR Core Examination will share the expectation of physics teaching from a resident perspective.

The lecture will help develop robust educational approaches to prepare radiology residents for safer and more effective lifelong practice.

Learning Objectives:

Learn updated physics requirements for radiology residents

Pursue effective approaches to teach physics to radiology residents

Learn expectation of physics teaching from resident perspective

J. Zhang, This topic is partially supported by RSNA Education Scholar Grant
TH‐EF‐BRA‐04: Individually Optimized Contrast‐Enhanced 4D‐CT for Radiotherapy Simulation in Pancreatic Ductal Adenocarcinoma
Authors: Choi W , Xue M , Lane B , Kang M , Patel K , Regine W , Klahr P , Wang J , Chen S , D'souza W , Lu W
Published: July 2016

Purpose:

To develop an individually optimized contrast‐enhanced (CE) 4D‐CT for radiotherapy simulation in pancreatic ductal adenocarcinomas (PDA).

Methods:

Ten PDA patients were enrolled. Each underwent 3 CT scans: a 4D‐CT immediately following a CE 3D‐CT and an individually optimized CE 4D‐CT using test injection. Three physicians contoured the tumor and pancreatic tissues. We compared image quality scores, tumor volume, motion, tumor‐to‐pancreas contrast, and contrast‐to‐noise ratio (CNR) in the 3 CTs. We also evaluated interobserver variations in contouring the tumor using simultaneous truth and performance level estimation (STAPLE).

Results:

Average image quality scores for CE 3DCT and CE 4D‐CT were comparable (4.0 and 3.8, respectively; P=0.47), and both were significantly better than that for 4D‐CT (2.6, P<0.001). Tumor‐to‐pancreas contrast results were comparable in CE 3D‐CT and CE 4D‐CT (15.5 and 16.7 HU, respectively; P=0.71), and the latter was significantly higher than in 4D‐CT (9.2 HU, P=0.03). Image noise in CE 3D‐CT (12.5 HU) was significantly lower than in CE 4D‐CT (22.1 HU, P<0.001) and 4D‐CT (19.4 HU, P=0.005). CNRs were comparable in CE 3D‐CT and CE 4DCT (1.4 and 0.8, respectively; P=0.23), and the former was significantly better than in 4D‐CT (0.6, P = 0.04). Mean tumor volumes were smaller in CE 3D‐CT (29.8 cm3) and CE 4D‐CT (22.8 cm3) than in 4D‐CT (42.0 cm3), although these differences were not statistically significant. Mean tumor motion was comparable in 4D‐CT and CE 4D‐CT (7.2 and 6.2 mm, P=0.23). Interobserver variations were comparable in CE 3D‐CT and CE 4D‐CT (Jaccard index 66.0% and 61.9%, respectively) and were worse for 4D‐CT (55.6%) than CE 3D‐CT.

Conclusion:

CE 4D‐CT demonstrated characteristics comparable to CE 3D‐CT, with high potential for simultaneously delineating the tumor and quantifying tumor motion with a single scan.

Supported in part by Philips Healthcare.
TH‐EF‐BRA‐07: Evaluation of Internal Target Volume Derived From a Prototype 4D‐MRI Sequence with 3D Radial Stack‐Of‐Stars Trajectory and K‐Space Self‐Gating
Authors: Yang W , Fan Z , Deng Z , Pang J , Bi X , Fenchel M , Li D , Fraass B , Hakimian B , Reznik R , Bryant M , Sandler H , Tuli R
Published: July 2016

Purpose:

4D‐MRI based on resorting of 2D‐cine‐MRI images shows great potential to assess tumor motion more accurately compared to 4D‐CT, however, it suffers from low through‐plane resolution and stitching artifacts. 4D‐MRI based on 3D acquisition results in stitching‐artifact‐free images with high in‐plane and through‐plane resolutions. In this study, we report our early clinical experience of a prototype 4D‐MRI sequence with 3D stack‐of‐stars (SOS) trajectory for internal target volume (ITV) definition.

Methods:

Ten patients with 13 total lesions (7 pancreatic, 1 lung with 2 lesions, 1 liver with 3 lesions and 1 esophagus) were recruited. 4D‐MRI used in‐plane radial and through‐plane Cartesian sampling. Two imaging orientations, i.e. axial slab (A) and coronal slab (B), were compared. ITVs were derived from 3‐bin (ITV3), 5‐bin (ITV5) and 10‐bin (ITV10) reconstruction protocols. ITV5 was set as standard and minimum expansion of ITV3 needed to encompass ITV5 was derived. Similarity index was calculated from ITV3 and ITV5 (SI3/5), and ITV10 and ITV5 (SI10/5). Imaging noise was calculated for both method A and B. Wilcoxon‐rank‐sum test was performed with a p value <0.05 deemed as significant.

Results:

No significant difference (p=0.34) was observed from method A and B, indicating a uniform imaging noise distribution from 3D acquisition. Imaging noise and artifacts were visually different from different binning protocols, with more bins resulting in more noise, more artifacts and larger ITV. On average, ITV differs by 7% (1%–19%) comparing ITV3 with ITV5 for the patient cohort. For the pancreas sub‐group, ITV differs by 4% (1%–6%). An average of 2.3mm (2mm‐3mm) expansion was needed for ITV3 to encompass ITV5. SI10/5 was 0.93±0.03 (mean±σ) and SI3/5 was 0.95±0.03.

Conclusion:

4D‐MRI with 3D SOS trajectory was evaluated on 10 patients. Significant difference in ITV was observed with different binning protocols. Imaging noise was similar irrespective of the imaging orientations.

This work is partially supported by NIH R03CA173273 and CTSI core voucher award.
TH‐E‐202‐02: The Use of Hypoxia PET Imaging for Radiotherapy
Authors: Humm J.
Published: July 2016

PET/CT is a very important imaging tool in the management of oncology patients. PET/CT has been applied for treatment planning and response evaluation in radiation therapy. This educational session will discuss:

Pitfalls and remedies in PET/CT imaging for RT planning

The use of hypoxia PET imaging for radiotherapy

PET for tumor response evaluation

The first presentation will address the issue of mis‐registration between the CT and PET images in the thorax and the abdomen. We will discuss the challenges of respiratory gating and introduce an average CT technique to improve the registration for dose calculation and image‐guidance in radiation therapy. The second presentation will discuss the use of hypoxia PET Imaging for radiation therapy. We will discuss various hypoxia radiotracers, the choice of clinical acquisition protocol (in particular a single late static acquisition versus a dynamic acquisition), and the compartmental modeling with different transfer rate constants explained. We will demonstrate applications of hypoxia imaging for dose escalation/de‐escalation in clinical trials. The last presentation will discuss the use of PET/CT for tumor response evaluation. We will discuss anatomic response assessment vs. metabolic response assessment, visual evaluation and semi‐quantitative evaluation, and limitations of current PET/CT assessment. We will summarize clinical trials using PET response in guiding adaptive radiotherapy. Finally, we will summarize recent advancements in PET/CT radiomics and non‐FDG PET tracers for response assessment.

Learning Objectives:

Identify the causes of mis‐registration of CT and PET images in PET/CT, and review the strategies to remedy the issue.

Understand the basics of PET imaging of tumor hypoxia (radiotracers, how PET measures the hypoxia selective uptake, imaging protocols, applications in chemo‐radiation therapy).

Understand the basics of dynamic PET imaging, compartmental modeling and parametric images.

Understand the basics of using FDG PET/CT for tumor response evaluation.

Learn about recent advancement in PET/CT radiomics and non‐FDG PET tracers for response assessment.

This work was supported in part by the National Cancer Institute Grants R01CA172638.; W. Lu, This work was supported in part by the National Cancer Institute Grants R01CA172638.
TH‐EF‐207A‐05: Feasibility of Applying SMEIR Method On Small Animal 4D Cone Beam CT Imaging
Authors: Zhong Y , Zhang Y , Shao Y , Wang J
Published: July 2016

Purpose:

Small animal cone beam CT imaging has been widely used in preclinical research. Due to the higher respiratory rate and heat beats of small animals, motion blurring is inevitable and needs to be corrected in the reconstruction. Simultaneous motion estimation and image reconstruction (SMEIR) method, which uses projection images of all phases, proved to be effective in motion model estimation and able to reconstruct motion‐compensated images. We demonstrate the application of SMEIR for small animal 4D cone beam CT imaging by computer simulations on a digital rat model.

Methods:

The small animal CBCT imaging system was simulated with the source‐to‐detector distance of 300 mm and the source‐to‐object distance of 200 mm. A sequence of rat phantom were generated with 0.4 mm3 voxel size. The respiratory cycle was taken as 1.0 second and the motions were simulated with a diaphragm motion of 2.4mm and an anterior‐posterior expansion of 1.6 mm. The projection images were calculated using a ray‐tracing method, and 4D‐CBCT were reconstructed using SMEIR and FDK methods. The SMEIR method iterates over two alternating steps: 1) motion‐compensated iterative image reconstruction by using projections from all respiration phases and 2) motion model estimation from projections directly through a 2D‐3D deformable registration of the image obtained in the first step to projection images of other phases.

Results:

The images reconstructed using SMEIR method reproduced the features in the original phantom. Projections from the same phase were also reconstructed using FDK method. Compared with the FDK results, the images from SMEIR method substantially improve the image quality with minimum artifacts.

Conclusion:

We demonstrate that it is viable to apply SMEIR method to reconstruct small animal 4D‐CBCT images.
TH‐F‐202‐02: Current Applications of MRI in Radiotherapy
Authors: Li G.
Published: July 2016

MRI has excellent soft tissue contrast and can provide both anatomical and physiological information. It is becoming increasingly important in radiation therapy for treatment planning, image‐guided radiation therapy, and treatment assessment. It is critically important at this time point to educate and update our medical physicists about MRI to prepare for the upcoming surge of MRI applications in radiation therapy. This session will review important basics of MR physics, pulse sequence designs, and current radiotherapy application, as well as showcase exciting new developments in MRI that can be potentially useful in radiation therapy.

Learning Objectives:

To learn basics of MR physics and understand the differences between various pulse sequences

To review current applications of MRI in radiation therapy.To discuss recent MRI advances for future MRI guided radiation therapy

Partly supported by NIH (1R21CA165384).; W. Miller, Research supported in part by Siemens Healthcare; G. Li, My clinical research is in part supported by NIH U54CA137788. I have a collaborative research project with Philips Healthcare.; J. Cai, jing cai
Bowhead whale localization using asynchronous hydrophones in the Chukchi Sea
Authors: Warner Graham A. , Dosso Stan E. , Hannay David E. , Dettmer Jan
Published: July 2016

This paper estimates bowhead whale locations and uncertainties using non-linear Bayesian inversion of their modally-dispersed calls recorded on asynchronous recorders in the Chukchi Sea, Alaska. Bowhead calls were recorded on a cluster of 7 asynchronous ocean-bottom hydrophones that were separated by 0.5–9.2 km. A warping time-frequency analysis is used to extract relative mode arrival times as a function of frequency for nine frequency-modulated whale calls that dispersed in the shallow water environment. Each call was recorded on multiple hydrophones and the mode arrival times are inverted for: the whale location in the horizontal plane, source instantaneous frequency (IF), water sound-speed profile, seabed geoacoustic parameters, relative recorder clock drifts, and residual error standard deviations, all with estimated uncertainties. A simulation study shows that accurate prior environmental knowledge is not required for accurate localization as long as the inversion treats the environment as unknown. Joint inversion of multiple recorded calls is shown to substantially reduce uncertainties in location, source IF, and relative clock drift. Whale location uncertainties are estimated to be 30–160 m and relative clock drift uncertainties are 3–26 ms.
Ca
2+
controls gating of voltage-gated calcium channels by releasing the β2e subunit from the plasma membrane
Authors: Kim Dong-Il , Kweon Hae-Jin , Park Yongsoo , Jang Deok-Jin , Suh Byung-Chang
Published: July 2016

The β2e subunit of voltage-gated calcium channels is uniquely suited to integrate G protein–coupled receptor signals with calcium channel activity.
Mapping the subcellular mechanical properties of live cells in tissues with fluorescence emission–Brillouin imaging
Authors: Elsayad Kareem , Werner Stephanie , Gallemí Marçal , Kong Jixiang , Sánchez Guajardo Edmundo R. , Zhang Lijuan , Jaillais Yvon , Greb Thomas , Belkhadir Youssef
Published: July 2016

Fluorescence-Brillouin imaging reveals that plants regulate the mechanical properties of the extracellular matrix in response to light.
Mixed-up Hippos don’t inhibit cell growth
Authors: VanHook Annalisa M.
Published: July 2016

The Hippo homologs MST1 and MST2 form heterodimers that do not repress cell proliferation.
Papers of note in
Science
Authors: VanHook Annalisa M.
Published: July 2016

This week’s articles highlight the structural biology of a neurotransmitter receptor, the posttranslational modification of proteins by ADP-ribosylation, maintenance of the proteome, elimination of centrioles during oogenesis, and a protein that promotes engraftment of transplanted photoreceptor cells.
Papers of note in
Science Translational Medicine
Authors: Ferrarelli Leslie K.
Published: July 2016

This week’s article and associated coverage describe how molecules on the surface of endothelial cells could focus the delivery of drugs to tumors.
Salmonella spondylodiscitis of the thoracic vertebrae mimicking spine tuberculosis
Authors: Muhamad Effendi Ferdhany , Ibrahim Mohd Ikraam , Mohd Miswan Mohd Fairudz
Published: July 2016

ExtraintestinalSalmonellainfection involving the thoracic spine is very rare. It commonly presents with non-specific chronic back pain and can occur with no gastrointestinal manifestation. Blood test results and imaging findings are often indistinguishable from more common chronic spine infections such as spine tuberculosis. Culture studies remain the key to establishing a definitive diagnosis and subsequently successful treatment. We report a case in which a patient presented with symptoms and signs suggestive of spine tuberculosis, yet the culture examination revealed otherwise.
Hypopyon uveitis following panretinal photocoagulation
Authors: Tyagi Mudit , Ambiya Vikas , Rani Padmaja Kumari
Published: July 2016

We report the case of a 58-year-old man with proliferative diabetic retinopathy in both eyes, and a history of recurrent anterior uveitis in the right eye, who underwent panretinal laser photocoagulation (PRP) for the retinopathy in both eyes, following which he developed hypopyon uveitis in the right eye. The condition was managed with topical steroids and cycloplegics, to which he readily responded. The case highlights that there is a breakdown of the blood aqueous barrier consequent to PRP. Patients with a history of uveitis are predisposed to develop recurrent uveitis after the said procedure and should be closely watched for such complications.
Working memory is limited: improving knowledge transfer by optimising simulation through cognitive load theory
Authors: Meguerdichian Michael , Walker Katie , Bajaj Komal
Published: July 2016

This analysis explores how to optimise knowledge transfer in healthcare simulation by applying cognitive load theory to curriculum design and delivery for both novice and expert learners. This is particularly relevant for interprofessional learning which is team-based, as each participant comes to the simulation experience with different levels of expertise. Healthcare simulation can offer opportunities to create complex and dynamic experiences that replicate real clinical situations. Understanding Cognitive Load Theory can foster the acquisition of complex knowledge, skills and abilities required to deliver excellence in patient care without overwhelming a learner's ability to handle new materials due to working memory limitations. The 2 aspects of working memory that will be explored in this paper are intrinsic load and extrinsic load. These will be addressed in terms of the learner's level of expertise and how to consider these elements to enhance the learning environment in simulation scenario development and delivery. By applying the concepts of Cognitive Load Theory, this paper offers educators a method to tailor their curricula to navigate working memory and optimise the opportunity for knowledge transfer.
Water slide injuries in Jamaica
Authors: Fletcher Cary K , McDowell Derrick
Published: July 2016

Background

Patients are presented in this study to describe injuries, each of which have not been previously described in the literature, as a result of a specific mechanism of injury on a water slide. Some of these injuries are potentially fatal and are usually the result of a very high energy mechanism of injury. All injuries occurred in a 6-week time span in the summer of 2015.

Method

Injuries arising from water slides and their definitive treatment were documented. All of the cases presented to Saint Ann's Bay Hospital in Saint Ann's Bay, Jamaica. The mechanism of injury was analyzed with a view to implement preventative measures.

Results

Three cases had open book pelvic injuries and one of them also had a vaginal tear. All of the open book injuries occurred after the patron's thighs violently abducted despite adhering to the recommended starting position that suggested patrons cross their legs. The fourth case was of a 25-year-old man who sustained a posterior shoulder dislocation as a result of his arms flailing despite attempting to adhere to the rule recommending that the patron place his arms across his chest. The final case was of a 14-year-old boy who was involved in an atypical collision injury, resulting in the boy sustaining a displaced distal femoral fracture.

Conclusions

Modern water slides will expose patrons to more frequent and severe injuries from atypical mechanisms of injuries. Risk factors for injury must be factored into preventative measures. Improved surveillance strategies to monitor these injuries are suggested.
Eigenvalue Expansion Approach to Study Bio-Heat Equation
Authors: Khanday M. A. , Nazir Khalid
Published: July 2016

A mathematical model based on Pennes bio-heat equation was formulated to estimate temperature profiles at peripheral regions of human body. The heat processes due to diffusion, perfusion and metabolic pathways were considered to establish the second-order partial differential equation together with initial and boundary conditions. The model was solved using eigenvalue method and the numerical values of the physiological parameters were used to understand the thermal disturbance on the biological tissues. The results were illustrated at atmospheric temperatures [Formula: see text]C and [Formula: see text]C.
Product Selection Problem
Authors: Xu Silei , Lui John C. S.
Published: July 2016

It is often crucial for manufacturers to decide what products to produce so that they can increase their market share in an increasingly fierce market. To decide which products to produce, manufacturers need to analyze the consumers’ requirements and how consumers make their purchase decisions so that the new products will be competitive in the market. In this paper, we first present a general distance-based product adoption model to capture consumers’ purchase behavior. Using this model, various distance metrics can be used to describe different real life purchase behavior. We then provide a learning algorithm to decide which set of distance metrics one should use when we are given some accessible historical purchase data. Based on the product adoption model, we formalize the

k most marketable products (or k-
MMP
)

selection problem and formally prove that the problem is
NP-hard
. To tackle this problem, we propose an efficient greedy-based approximation algorithm with a provable solution guarantee. Using submodularity analysis, we prove that our approximation algorithm can achieve at least 63% of the optimal solution. We apply our algorithm on both synthetic datasets and real-world datasets (TripAdvisor.com), and show that our algorithm can easily achieve five or more orders of speedup over the exhaustive search and achieve about 96% of the optimal solution on average. Our experiments also demonstrate the robustness of our distance metric learning method, and illustrate how one can adopt it to improve the accuracy of product selection.
Manycore Algorithms for Batch Scalar and Block Tridiagonal Solvers
Authors: László Endre , Giles Mike , Appleyard Jeremy
Published: July 2016

Engineering, scientific, and financial applications often require the simultaneous solution of a large number of independent tridiagonal systems of equations with varying coefficients. Since the number of systems is large enough to offer considerable parallelism on manycore systems, the choice between different tridiagonal solution algorithms, such as Thomas, Cyclic Reduction (CR) or Parallel Cyclic Reduction (PCR) needs to be reexamined. This work investigates the optimal choice of tridiagonal algorithm for CPU, Intel MIC, and NVIDIA GPU with a focus on minimizing the amount of data transfer to and from the main memory using novel algorithms and the register-blocking mechanism, and maximizing the achieved bandwidth. It also considers block tridiagonal solutions, which are sometimes required in Computational Fluid Dynamic (CFD) applications. A novel work-sharing and register blocking--based Thomas solver is also presented.
Printed Perforated Lampshades for Continuous Projective Images
Authors: Zhao Haisen , Lu Lin , Wei Yuan , Lischinski Dani , Sharf Andrei , Cohen-Or Daniel , Chen Baoquan
Published: July 2016

We present a technique for designing three-dimensional- (3D) printed perforated lampshades that project continuous grayscale images onto the surrounding walls. Given the geometry of the lampshade and a target grayscale image, our method computes a distribution of tiny holes over the shell, such that the combined footprints of the light emanating through the holes form the target image on a nearby diffuse surface. Our objective is to approximate the continuous tones and the spatial detail of the target image to the extent possible within the constraints of the fabrication process.

To ensure structural integrity, there are lower bounds on the thickness of the shell, the radii of the holes, and the minimal distances between adjacent holes. Thus, the holes are realized as thin tubes distributed over the lampshade surface. The amount of light passing through a single tube may be controlled by the tube’s radius and by its orientation (tilt angle). The core of our technique thus consists of determining a suitable configuration of the tubes: their distribution across the relevant portion of the lampshade, as well as the parameters (radius, tilt angle) of each tube. This is achieved by computing a capacity-constrained Voronoi tessellation over a suitably defined density function and embedding a tube inside the maximal inscribed circle of each tessellation cell.
Survey On Software Design-Pattern Specification Languages
Authors: Khwaja Salman , Alshayeb Mohammad
Published: July 2016

A design pattern is a well-defined solution to a recurrent problem. Over the years, the number of patterns and domains of design patterns have expanded, as the patterns are the experiences of the experts of the domain captured in a higher-level abstraction. This led others to work on languages for design patterns to systematically document abstraction detailed in the design pattern rather than capture algorithms and data. These design-pattern specification languages come in different flavors, targeting different aspects of design patterns. Some design-pattern specification languages tried to capture the description of the design pattern in graphical or textual format, others tried to discover design patterns in code or design diagrams, and still other design-pattern specification languages have other objectives. However, so far, no effort has been made to compare these design-pattern specification languages and identify their strengths and weaknesses. This article provides a survey and a comparison between existing design-pattern specification languages using a design-pattern specification language evaluation framework. Analysis is done by grouping the design-pattern specification languages into different categories. In addition, a brief description is provided regarding the tools available for the design-pattern specification languages. Finally, we identify some open research issues that still need to be resolved.
Educating for HCI at scale
Authors: Rosenberg Daniel
Published: July 2016

HCI education reflects the continual evolution of HCI, embracing the changing landscapes of technology, infrastructure, and technology use. This forum aims to provide a platform for HCI educators, practitioners, researchers, and students to share their perspectives, reflections, and experiences related to HCI education.
--- Sukeshini Grandhi, Editor
Multi-Criteria Code Refactoring Using Search-Based Software Engineering
Authors: Ouni Ali , Kessentini Marouane , Sahraoui Houari , Inoue Katsuro , Deb Kalyanmoy
Published: July 2016

One of the most widely used techniques to improve the quality of existing software systems is refactoring—the process of improving the design of existing code by changing its internal structure without altering its external behavior. While it is important to suggest refactorings that improve the quality and structure of the system, many other criteria are also important to consider, such as reducing the number of code changes, preserving the semantics of the software design and not only its behavior, and maintaining consistency with the previously applied refactorings. In this article, we propose a multi-objective search-based approach for automating the recommendation of refactorings. The process aims at finding the optimal sequence of refactorings that (i) improves the quality by minimizing the number of design defects, (ii) minimizes code changes required to fix those defects, (iii) preserves design semantics, and (iv) maximizes the consistency with the previously code changes. We evaluated the efficiency of our approach using a benchmark of six open-source systems, 11 different types of refactorings (move method, move field, pull up method, pull up field, push down method, push down field, inline class, move class, extract class, extract method, and extract interface) and six commonly occurring design defect types (blob, spaghetti code, functional decomposition, data class, shotgun surgery, and feature envy) through an empirical study conducted with experts. In addition, we performed an industrial validation of our technique, with 10 software engineers, on a large project provided by our industrial partner. We found that the proposed refactorings succeed in preserving the design coherence of the code, with an acceptable level of code change score while reusing knowledge from recorded refactorings applied in the past to similar contexts.
A Survey and Comparative Study of Tweet Sentiment Analysis via Semi-Supervised Learning
Authors: Silva Nadia Felix F. Da , Coletta Luiz F. S. , Hruschka Eduardo R.
Published: July 2016

Twitter is a microblogging platform in which users can post status messages, called “tweets,” to their friends. It has provided an enormous dataset of the so-called sentiments, whose classification can take place through supervised learning. To build supervised learning models, classification algorithms require a set of representative labeled data. However, labeled data are usually difficult and expensive to obtain, which motivates the interest in semi-supervised learning. This type of learning uses unlabeled data to complement the information provided by the labeled data in the training process; therefore, it is particularly useful in applications including tweet sentiment analysis, where a huge quantity of unlabeled data is accessible. Semi-supervised learning for tweet sentiment analysis, although appealing, is relatively new. We provide a comprehensive survey of semi-supervised approaches applied to tweet classification. Such approaches consist of graph-based, wrapper-based, and topic-based methods. A comparative study of algorithms based on self-training, co-training, topic modeling, and distant supervision highlights their biases and sheds light on aspects that the practitioner should consider in real-world applications.
A Virtualized Separation Kernel for Mixed-Criticality Systems
Authors: West Richard , Li Ye , Missimer Eric , Danish Matthew
Published: July 2016

Multi- and many-core processors are becoming increasingly popular in embedded systems. Many of these processors now feature hardware virtualization capabilities, as found on the ARM Cortex A15 and x86 architectures with Intel VT-x or AMD-V support. Hardware virtualization provides a way to partition physical resources, including processor cores, memory, and I/O devices, among guest virtual machines (VMs). Each VM is then able to host tasks of a specific criticality level, as part of a mixed-criticality system with different timing and safety requirements. However, traditional virtual machine systems are inappropriate for mixed-criticality computing. They use hypervisors to schedule separate VMs on physical processor cores. The costs of trapping into hypervisors to multiplex and manage machine physical resources on behalf of separate guests are too expensive for many time-critical tasks. Additionally, traditional hypervisors have memory footprints that are often too large for many embedded computing systems. In this article, we discuss the design of the Quest-V separation kernel, which partitions services of different criticality levels across separate VMs, or
sandboxes
. Each sandbox encapsulates a subset of machine physical resources that it manages without requiring intervention from a hypervisor. In Quest-V, a hypervisor is only needed to bootstrap the system, recover from certain faults, and establish communication channels between sandboxes. This not only reduces the memory footprint of the most privileged protection domain but also removes it from the control path during normal system operation, thereby heightening security.
A Survey on Thread-Level Speculation Techniques
Authors: Estebanez Alvaro , Llanos Diego R. , Gonzalez-Escribano Arturo
Published: July 2016

Thread-Level Speculation (TLS) is a promising technique that allows the parallel execution of sequential code without relying on a prior, compile-time-dependence analysis. In this work, we introduce the technique, present a taxonomy of TLS solutions, and summarize and put into perspective the most relevant advances in this field.
Target Tracking for Sensor Networks
Authors: Souza Éfren L. , Nakamura Eduardo F. , Pazzi Richard W.
Published: July 2016

Target-tracking algorithms typically organize the network into a logical structure (e.g., tree, cluster, or faces) to enable data fusion and reduce communication costs. These algorithms often predict the target’s future position. In addition to using position forecasts for decision making, we can also use such information to save energy by activating only the set of sensors nearby the target’s trajectory. In this work, we survey of the state of the art of target-tracking techniques in sensor networks. We identify three different formulations for the target-tracking problem and classify the target-tracking algorithms based on common characteristics. Furthermore, for the sake of a better understanding of the target-tracking process, we organize this process in six components: target detection, node cooperation, position computation, future-position estimation, energy management, and target recovery. Each component has different solutions that affect the target-tracking performance.
Introduction
Authors: North Steve , Mancini Clara
Published: July 2016

Animal-computer interaction (ACI) [1] is an emerging discipline concerned with studying the relationship between animals and technology, designing interactive technology to support animals, and developing methodologies that can enable animals to participate in the design process as legitimate stakeholders. By welcoming animals to the design table, ACI is delineating new frontiers for interaction design. However, if co-designing HCI artifacts is already fraught with misunderstanding, how might ACI researchers hope to design
for
and
with
other species? It is this key question that the contributions to this Special Topic on ACI address from different perspectives.
Steve North
and
Clara Mancini
, Special Topic Editors
Understanding Latency Variation in Modern DRAM Chips
Authors: Chang Kevin K. , Kashyap Abhijith , Hassan Hasan , Ghose Saugata , Hsieh Kevin , Lee Donghyuk , Li Tianshi , Pekhimenko Gennady , Khan Samira , Mutlu Onur
Published: July 2016

Long DRAM latency is a critical performance bottleneck in current systems. DRAM access latency is defined by three fundamental operations that take place within the DRAM cell array: (i) activation of a memory row, which opens the row to perform accesses; (ii) precharge, which prepares the cell array for the next memory access; and (iii) restoration of the row, which restores the values of cells in the row that were destroyed due to activation. There is significant latency variation for each of these operations across the cells of a single DRAM chip due to irregularity in the manufacturing process. As a result, some cells are inherently faster to access, while others are inherently slower. Unfortunately, existing systems do not exploit this variation.

The goal of this work is to (i) experimentally characterize and understand the latency variation across cells within a DRAM chip for these three fundamental DRAM operations, and (ii) develop new mechanisms that exploit our understanding of the latency variation to reliably improve performance. To this end, we comprehensively characterize 240 DRAM chips from three major vendors, and make several new observations about latency variation within DRAM. We find that (i) there is large latency variation across the cells for each of the three operations; (ii) variation characteristics exhibit significant spatial locality: slower cells are clustered in certain regions of a DRAM chip; and (iii) the three fundamental operations exhibit different reliability characteristics when the latency of each operation is reduced.

Based on our observations, we propose Flexible-LatencY DRAM (FLY-DRAM), a mechanism that exploits latency variation across DRAM cells within a DRAM chip to improve system performance. The key idea of FLY-DRAM is to exploit the spatial locality of slower cells within DRAM, and access the faster DRAM regions with reduced latencies for the fundamental operations. Our evaluations show that FLY-DRAM improves the performance of a wide range of applications by 13.3%, 17.6%, and 19.5%, on average, for each of the three different vendors' real DRAM chips, in a simulated 8-core system. We conclude that the experimental characterization and analysis of latency variation within modern DRAM, provided by this work, can lead to new techniques that improve DRAM and system performance.
Achieving Low-Delay and Fast-Convergence in Stochastic Network Optimization
Authors: Liu Jia
Published: July 2016

Due to the rapid growth of mobile data demands, there have been significant interests in stochastic resource control and optimization for wireless networks. Although significant advances have been made in stochastic network optimization theory, to date, most of the existing approaches are plagued by either slow convergence or unsatisfactory delay performances. To address these challenges, in this paper, we develop a new stochastic network optimization framework inspired by the Nesterov accelerated gradient method. We show that our proposed Nesterovian approach offers utility-optimality, fast-convergence, and significant delay reduction in stochastic network optimization. Our contributions in this paper are three-fold: i) we propose a Nesterovian joint congestion control and routing/scheduling framework for both single-hop and multi-hop wireless networks; ii) we establish the utility optimality and queueing stability of the proposed Nesterovian method, and analytically characterize its delay reduction and convergence speed; and iii) we show that the proposed Nesterovian approach offers a three-way performance control between utility-optimality, delay, and convergence.
Delay, Memory, and Messaging Tradeoffs in Distributed Service Systems
Authors: Gamarnik David , Tsitsiklis John N. , Zubeldia Martin
Published: July 2016

We consider the following distributed service model: jobs with unit mean, exponentially distributed, and independent processing times arrive as a Poisson process of rate λ N, with 0<λ<1, and are immediately dispatched to one of several queues associated with N identical servers with unit processing rate. We assume that the dispatching decisions are made by a central dispatcher endowed with a finite memory, and with the ability to exchange messages with the servers. We study the fundamental resource requirements (memory bits and message exchange rate), in order to drive the expected steady-state queueing delay of a typical job to zero, as N increases. We propose a certain policy and establish (using a fluid limit approach) that it drives the delay to zero when either (i) the message rate grows superlinearly with N, or (ii) the memory grows superlogarithmically with N. Moreover, we show that any policy that has a certain symmetry property, and for which neither condition (i) or (ii) holds, results in an expected queueing delay which is bounded away from zero.

Finally, using the fluid limit approach once more, we show that for any given α>0 (no matter how small), if the policy only uses a linear message rate α N, the resulting asymptotic (as N->∞) expected queueing delay is positive but upper bounded, uniformly over all λ>1. This is a significant improvement over the popular "power-of-d-choices" policy, which has a limiting expected delay that grows as log ←(1/(1-λ)→) when λ↑ 1.
Towards Multi-Resource Fair Allocation with Placement Constraints
Authors: Wang Wei , Li Baochun , Liang Ben , Li Jun
Published: July 2016

Multi-resource fair schedulers have been widely implemented in compute clusters to provide service isolation guarantees. Existing multi-resource sharing policies, notably Dominant Resource Fairness (DRF) and its variants, are designed for unconstrained jobs that can run on all machines in a cluster. However, an increasing number of datacenter jobs specify placement constraints and can only run on a particular class of machines meeting specific hardware/software requirements (e.g., GPUs or a particular kernel version). We show that directly extending existing policies to constrained jobs either compromises isolation guarantees or allows users to gain more resources by deceiving the scheduler. It remains unclear how multi-resource fair sharing is defined and achieved in the presence of placement constraints. We address this open problem by a new sharing policy, called Task Share Fairness (TSF), that provides provable isolation guarantees and is strategy-proof against gaming the allocation policy. TSF is shown to be envy-free and Pareto optimal as well.