bluuebunny/crossref_metadata_2025 huggingface dataset:
Social media use in adolescents and young adults with serious illnesses: an integrative review
Authors: Peat George , Rodriguez Alison , Smith Joanna
Published: December 2018

Objectives

Adolescents and young adults with life-limiting or life-threatening conditions are often socially isolated because of the demands of their illness. Although adolescents and young adults have a noticeable online and social media presence, their motivations for using social media remain unclear. This article aims to summarise empirical research undertaken about how and why social media is used by adolescents and young adults with life-limiting or life-threatening conditions.

Methods

An integrative literature review was undertaken. Key healthcare research databases including CINHAL, MEDLINE and PSYCHINFO were searched for empirical studies reporting the use of social media by adolescents and young adults with life-limiting or life-threatening conditions. Fifteen articles met the inclusion criteria; included articles were quality appraised and a thematic synthesis undertaken to identify key themes.

Results

The reasons why adolescents and young adults with life-limiting or life-threatening conditions use social media are diverse, with differences relating to age and gender. However, this population in general uses social media to connect with others who have similar lived experiences.

Conclusion

Social media platforms can be useful adjuncts to the care of adolescents and young adults with life-limiting or life-threatening conditions. However, current evidence is dominated by studies on social media use by adolescents and young adults with cancer. More research is required to gain a holistic understanding of how and why social media is used by this population and its perceived benefits and limitations.
Right ventricular fibrosis is associated with cardiac remodelling after pulmonary valve replacement
Authors: Yamamura Kenichiro , Yuen Darren , Hickey Edward J , He Xiaolin , Chaturvedi Rajiv R , Friedberg Mark K , Grosse-Wortmann Lars , Hanneman Kate , Billia Filio , Farkouh Michael E , Wald Rachel M
Published: December 2018

Objective

The relationship between right ventricular (RV) fibrosis and right heart reverse remodelling following pulmonary valve replacement (PVR) has not been well studied in adults with repaired tetralogy of Fallot (rTOF). Our aims were to histologically quantify RV fibrosis and to explore the relationship between fibrosis severity and cardiac remodelling post-PVR.

Methods

Adults with rTOF and pre-PVR cardiovascular (CMR) imaging were consented to procurement of RV muscle during PVR. Samples were stained with picrosirius red to quantify collagen volume fraction. Clinical data at baseline and at last follow-up were reviewed. Adverse cardiovascular outcomes included death, sustained arrhythmia and heart failure.

Results

Fifty-three patients (male 58%, 38±11 years) were studied. Those with severe fibrosis (collagen volume fraction >11.0%, n=13) had longer aortic cross-clamp times at initial repair compared with the remainder of the population (50 vs 33 min, p=0.018) and increased RV mass:volume ratio pre-PVR (0.20 vs 0.18 g/mL, p=0.028). Post-PVR, the severe fibrosis group had increased indexed RV end-systolic volume index (RVESVi) (74 vs 66 mL/m2, p=0.044), decreased RVESVi change (Δ29 vs Δ45 mL/m2, p=0.005), increased RV mass (34 vs 25 g/m2, p=0.023) and larger right atrial (RA) area (21 vs 17 cm2, p=0.021). A trend towards increased heart failure events was observed in the severe fibrosis group (15% vs 0%, p=0.057).

Conclusions

Severe RV fibrosis was associated with increased RVESVi, RV mass and RA area post-PVR in rTOF. Further study is required to define the impact of fibrosis and persistent right heart enlargement on clinical outcomes.
Adherence to guidelines in management of symptoms suggestive of heart failure in primary care
Authors: Hayhoe Benedict , Kim Dani , Aylin Paul P , Majeed F Azeem , Cowie Martin R , Bottle Alex
Published: December 2018

Objective

Clinical guidelines on heart failure (HF) suggest timings for investigation and referral in primary care. We calculated the time for patients to achieve key elements in the recommended pathway to diagnosis of HF.

Methods

In this observational study, we used linked primary and secondary care data (Clinical Practice Research Datalink, a database of anonymised electronic records from UK general practices) between 2010 and 2013. Records were examined for presenting symptoms (breathlessness, fatigue, ankle swelling) and key elements of the National Institute for Health and Care Excellence-recommended pathway to diagnosis (serum natriuretic peptide (NP) test, echocardiography, specialist referral).

Results

42 403 patients were diagnosed with HF, of whom 16 597 presented in primary care with suggestive symptoms. 6464 (39%) had recorded NP or echocardiography, and 6043 (36%) specialist referral. Median time from recorded symptom(s) to investigation (NP or echocardiography) was 292 days (IQR 34–844) and to referral 236 days (IQR 42–721). Median time from symptom(s) to diagnosis was 972 days (IQR 337–1468) and to treatment with HF-relevant medication 803 days (IQR 230–1364). Factors significantly affecting timing of referral, treatment and diagnosis included patients’ sex (p=0.001), age (p<0.001), deprivation score (p=0.001), comorbidities (p<0.001) and presenting symptom type (p<0.001).

Conclusions

Median times to investigation or referral of patients presenting in primary care with symptoms suggestive of HF considerably exceeded recommendations. There is a need to support clinicians in the diagnosis of HF in primary care, with improved access to investigation and specialist assessment to support timely management.
Evaluating the effectiveness and safety of the carotid Casper-RX stent for tandem lesions in acute ischemic stroke
Authors: Bartolini Bruno , Puccinelli Francesco , Mosimann Pascal J , Hajdu Steven D , Veunac Louis , Michel Patrik , Saliou Guillaume
Published: December 2018

Introduction

A new generation of carotid artery stents that use a dual micromesh layer to reduce embolic events during carotid artery stenting has recently been introduced. We aimed to analyze the effectiveness and safety of the new Casper-RX stent in patients experiencing acute ischemic stroke with large vessel intracranial occlusion associated with a tandem lesion (another carotid occlusion or severe stenosis).

Methods

We retrospectively analyzed all consecutive patients treated with carotid Casper-RX stents from our stroke registry. We analyzed clinical, angiographic, and neuroimaging data. Endpoints included acute intra-stent thrombus formation, stent occlusion prior to hospital discharge, 3 month modified Rankin Scale score (mRS), and symptomatic intracranial hemorrhage.

Results

21 patients were included: 10 patients had tandem carotid occlusions and 11 patients had severe carotid stenosis, 8 of whom had a hemodynamically significant stenosis. We observed acute in-stent thrombus formation in 11 patients. No stent occlusion occurred prior to hospital discharge. We report no stroke recurrence at 3 months but symptomatic intracranial hemorrhage in two patients. mRS score at 3 months was 0–2 (favorable) for 15 patients (71%), 3–5 for 3 patients, and 6 for 3 patients.

Conclusions

In the present series, we frequently observed clot formation during the procedure with Casper-RX stents, which required periprocedural intravenous infusion of anticoagulant and antiplatelet treatment. This motivated us, in the absence of a prospective randomized controlled study demonstrating the non-inferiority of micromesh dual layer stents compared with the single layer design, to discontinue using this stent type in acute stroke requiring carotid angioplasty.
Factors associated with prolonged treatment days, increased veterinary visits and complications in horses with subsolar abscesses
Authors: Cole Stephen D , Stefanovski Darko , Towl Simon , Boyle Ashley G
Published: December 2018

There is a lack of epidemiological studies about equine subsolar (hoof) abscesses even though they are among one of the most common causes of acute, severe lameness. The goals of this study were to (1) describe the equine subsolar abscess patient population of the University of Pennsylvania's New Bolton Center's Field Service and (2) to determine the factors that are associated with increased veterinary visits, prolonged treatment and complications. Descriptive statistics were performed on data collected from 160 cases of equine subsolar abscess. Inferential statistics were performed on a subset of those cases. No significant results were identified in relation to an increased number of veterinary visits. Poisson regression of days of treatment revealed that abscesses diagnosed in the summer (incidence rate ratio (IRR)=9.42, P<0.001) and abscesses found at the coronary band (IRR=3.21, P<0.001) were more likely to be treated for longer. Presence of a draining tract (IRR=0.73, P=0.017) and a higher lameness (IRR=0.30, P=0.01 for grade 3, IRR=0.1, P<0.001 for grades 4 and 5) score at presentation resulted in shortened treatment times. Abscesses affecting multiple portions of the digit were associated with an increased chance of complication. The study presented here is the first retrospective study on subsolar abscesses to the authors’ knowledge.
Cats with IRIS stage 1 and 2 chronic kidney disease maintain body weight and lean muscle mass when fed food having increased caloric density, and enhanced concentrations of carnitine and essential amino acids
Authors: Hall Jean A , Fritsch Dale A , Jewell Dennis E , Burris Patricia A , Gross Kathy L
Published: December 2018

A prospective, randomised, 6‐month feeding trial was performed in 28 adult cats with International Renal Interest Society (IRIS) stage 1 and 2 chronic kidney disease (CKD). All cats were assigned to either a control food: Royal Canin Renal Support A Feline, dry or a test food: Hill's Prescription Diet k/d Feline with chicken, dry. Food intake was recorded daily; body weight weekly; and serum, urine, dual‐energy x‐ray absorptiometry (DEXA) and body condition assessments were performed at 0, 1, 3 and 6 months. Twenty cats (9 control, 11 test group) completed the study according to protocol. Cats consuming control food had significant loss of body weight (n=14; mean, −13.0 per cent, P<0.0001) and lean body mass (LBM; mean, −11.1 per cent, P<0.0001) over the 6‐month feeding period, whereas cats consuming test food had a significant increase in body weight (n=14; mean, 5.8 per cent, P=0.003) and no change in LBM (P=0.42). Cats consumed 23 per cent more calories (P=0.05) when fed test food (mean, 207.1 kcal/day) compared with cats fed control food (mean, 168.0 kcal/day). Serum creatinine increased at a faster rate (P=0.0004) in cats consuming control food compared with cats consuming test food. Cats consuming test food had increased caloric and essential amino acid intake, increased body weight, stable biomarkers of kidney function and maintained LBM compared with cats consuming control food.
Effects of flavonoids from Allium mongolicum Regel as a dietary additive on meat quality and composition of fatty acids related to flavor in lambs
Authors: Liu Wangjing , Ding He , Erdene Khas , Chen Renwei , Mu Qier , Ao Changjin
Published: December 2018

Sixty male Small-tailed Han sheep (initial body weight: 42.5 ± 4.1 kg) were assigned randomly and averagely into four groups to evaluate effects of flavonoids extracted from Allium mongolicum Regel (AMR) on meat quality and composition of fatty acids related to flavor in longissimus dorsi muscle of lambs. Lambs of four groups were fed a basal control diet (C), and basal diet + three different amounts of flavonoids extracted from the AMR; those were 11 mg kg−1 (Flav 11), 22 mg kg−1 (Flav 22), or 33 mg kg−1 (Flav 33), respectively. Dressing percentage, loin eye area, cooking loss, and pressing loss were affected by treatments (P < 0.05). Percentage of intramuscular fat, the concentrations of eicosapentaenoic acid, C18:0, total saturated fatty acids, monounsaturated fatty acid, and 4-methyloctanoic acid in longissimus dorsi muscle were changed by treatments (P < 0.05). Addition of AMR to diet improved the meat quality and had favorable effects on fatty acid composition related to meat flavor in longissimus dorsi muscle.
Systematic exploration of the pH dependence of a peptide hydrogel
Authors: Falcone Natashya , Shao Tsuimy , Sun Xiaoyi , Kraatz Heinz-Bernhard
Published: December 2018

Stimuli-responsive peptide gels are a growing class of functional biomaterials that are involved in many applications in research. Here, we present a novel di-peptide hydrogel from the compound Boc–Phe–Trp–OH in various buffer and pH conditions. We examine the effects of different stimuli, including temperature and pH, on the mechanical strength of the gels through frequency rheology studies. We found that this hydrogelator is highly pH dependent, only forming a gel in a narrow range of pH 6–7. This hydrogelator hold promise for the development of new stimuli-responsive biomaterials for specific applications that require this type of specific stimuli.
LA-ICP-MS zircon U–Pb and sericite 40Ar/39Ar ages of the Songjianghe gold deposit in southeastern Jilin Province, Northeast China, and their geological significance
Authors: Zhang Xiao-Tian , Sun Jing-Gui , Yu Zheng-Tao , Song Quan-Heng
Published: December 2018

The Songjianghe deposit is a newly discovered altered gold deposit in the southeastern Jiapigou-Haigou Gold Metallogenic Belt (JHGMB) in southeastern Jilin Province of NE China. The host rocks were considered to be the Mesoproterozoic Seluohe Group, and the metallogenic epoch lacked accurate isotopic constraints. To determine the age and metallogenic setting of the deposit, we describe the geologic characteristics of the deposit and present the results of petrographic and geochronologic analyses of the host rocks and ores. The ore bodies are hosted within a suite of amphibolite facies metamorphic rocks superimposed by greenschist facies indicative of retrograde metamorphism. Zircon U–Pb dating results indicate that the host rocks belong to the Jiapigou Group that formed at the end of the Neoarchean (2543–2527 Ma). Subsequently, the rocks successively underwent metamorphism during the late Neoarchean (2521–2506 Ma), retrograde metamorphism caused by the closure of the Paleo-Asian Ocean during the late Permian to Early Triassic (262–250 Ma), and extension after the closure of the Paleo-Asian Ocean during the Late Triassic (231–210 Ma). Sericite 40Ar/39Ar dating results suggest that the Songjianghe deposit formed during the Late Jurassic between 157 Ma and 156 Ma. By combining these new insights with those of previous studies, we propose that the Songjianghe deposit is a mesothermal gold deposit and that mineralization occurred during the extensional period in the intermittent stage that followed the first subduction of the Paleo-Pacific Plate. All the gold deposits in the JHGMB formed from the late Permian to Early Cretaceous by multi-stage mineralization events that corresponded temporally with the tectonic evolution of the Paleo-Asian Ocean and the episodic subduction of the Paleo-Pacific Plate.
Structure and composition of Nycteribiidae and Streblidae flies on bats along an environmental gradient in northeastern Brazil
Authors: Barbier Eder , Graciolli Gustavo , Bernard Enrico
Published: December 2018

Bats can be parasitized by several arthropod groups, including ectoparasitic flies. The high host specificity is a common phenomenon between flies and bats. In recent years, more efforts have been employed to understand how environmental variables can influence richness and parasitic load (PL). However, many gaps still need to be filled to better understand this issue. We analyzed the PL of flies on bats sampled in three environments with different rain volume and vegetation types to verify if PL is correlated with rainfall and if there are differences in the PL on bats within and between environments. Overall, there was no correlation between rainfall and PL in the same environment, nor a difference between the three environments. When tested separately, Seba’s short-tailed bats (Carollia perspicillata (Linnaeus, 1758)) had a difference in prevalence of flies between environments and flat-faced fruit-eating bats (Artibeus planirostris (Spix, 1823)) had a greater abundance of flies in the rainy season in a semiarid area. There was no difference in PL between male and female bats. Our results suggest that bat–fly interactions are driven by several factors, not only by the amount of rainfall or vegetation, and that different host species may respond differently with no obvious general pattern.
Bound state solution of the Klein–Fock–Gordon equation with the Hulthén plus a ring-shaped-like potential within SUSY quantum mechanics
Authors: Ahmadov A. I. , Nagiyev Sh. M. , Qocayeva M. V. , Uzun K. , Tarverdiyeva V. A.
Published: December 2018

In this paper, the bound state solution of the modified Klein–Fock–Gordon equation is obtained for the Hulthén plus ring-shaped-like potential by using the developed scheme to overcome the centrifugal part. The energy eigenvalues and corresponding radial and azimuthal wave functions are defined for any [Formula: see text] angular momentum case on the conditions that scalar potential is whether equal and nonequal to vector potential, the bound state solutions of the Klein–Fock–Gordon equation of the Hulthén plus ring-shaped-like potential are obtained by Nikiforov–Uvarov (NU) and supersymmetric quantum mechanics (SUSY QM) methods. The equivalent expressions are obtained for the energy eigenvalues, and the expression of radial wave functions transformations to each other is revealed owing to both methods. The energy levels and the corresponding normalized eigenfunctions are represented in terms of the Jacobi polynomials for arbitrary [Formula: see text] states. A closed form of the normalization constant of the wave functions is also found. It is shown that the energy eigenvalues and eigenfunctions are sensitive to [Formula: see text] radial and [Formula: see text] orbital quantum numbers.
Colorimetric detection of solution concentration based on a paper-based microfluidic device
Authors: Dong Liangwei , Hu Yueli , Chen Xiuyu , Liu Xiajun
Published: December 2018

A new method for colorimetric detection of solution concentration is presented. A paper-based microfluidic device was designed and made using printed circuit board technology. Detection zone patterns were designed and transferred to a printed circuit board by hollowing technology. The printed circuit board with patterns was stuck onto a copper sheet. The hollowed zone was filled with solid paraffin and then covered with a piece of filter paper. The paraffin wax was melted by heating the copper sheet and permeated into the filter paper. Solution to be detected was pipetted on the paper-based device with detective zones. The images of the detective zones were obtained using a microscope with charge-coupled device, which is used for calculating RGBI model to further obtain the solution concentration. Litmus was demonstrated in sample experiments. Results showed that maximum error of measured value of solution concentration to its true value is less than 2% using the presented method.
Temporal spatial pulse signal detection system based on a flexible probe and binocular stereo vision
Authors: Yang LiMing , Zhang AiHua
Published: December 2018

The simulation of Chinese pulse diagnosis via acquisition and qualitative description of temporal and spatial pulse signals is important for objective pulse diagnosis in traditional Chinese medicine. In order to simulate pulse diagnosis by fingers, we developed a novel pulse signal detection device based on the airbag-type flexible probe, in which the pulse-taking pressure was adjusted using lever principle. A contact film was fixed at the tip of the probe, and two cameras were used to synchronously taking the deformation image of the contact film. Grid-pattern lines were printed on the contact film. Image coordinates of the intersection points were detected using ridge line fitting method. Then, the 3D coordinates of the intersection points were calculated based on binocular vision measurement principle and the deformations of the contact film was reconstructed through surface fitting. Finally, the 3D pulse image series containing spatial and temporal information were acquired. Using the acquired 3D pulse images, the pulse conditions can be quantitatively described, indicating the 3D pulse images are an effective way of quantitatively describing pulse conditions.
Some new soliton-like and doubly periodic-like solutions of Fisher equation with time-dependent coefficients
Authors: Abdel Latif M. S. , El-Shazly E. , Baleanu D. , Elsaid A. , Nour H. M.
Published: December 2018

In this paper, the group classification is presented for Fisher equation with time-dependent coefficients. The analysis provided many new solutions that take the form of doubly periodic-like solutions and soliton-like solutions.
Synthesis of α,α’-linked penta- and septaheterocycles by tandem Suzuki coupling
Authors: Zafar Hadiqa , Brewster James T. , Wight Christopher D. , McVeigh Matthew , Steinbrück Axel , Lynch Vincent M. , Sessler Jonathan L.
Published: December 2018

The controlled synthesis of oligoaromatics can provide materials of wide utility. Here, we describe the preparation of higher order oligoheterocycles via a tandem Suzuki cross-coupling protocol. This method has allowed for the iterative construction of fluorescent [Formula: see text],[Formula: see text]-linked penta- and septaheterocyclic systems with modification of the terminal moiety allowing for fine-tuning of the emission features.
Synthesis of vitamin B12 derivatives with sodium hydroxymethanesulfinate
Authors: Pugina Raida A. , Denisova Elena A. , Ivlev Pavel A. , Salnikov Denis S. , Makarov Sergei V.
Published: December 2018

The reaction of cyanocobalamin (CNCbl) with sodium hydroxymethanesulfinate (HMS) was studied over a wide range of pH (4–11) under aerobic conditions. CNCbl is destroyed in the presence of HMS in aqueous solution to form uncolored substances. The accumulation of stable yellow corrinoids (SYCs) preceded these changes at pH [Formula: see text] 8. The major stable yellow corrinoid is (15R)-Co[Formula: see text], Coß — dicyano-13-dehydro-15-hydro-l5-hydroxycob(III)alamin. The yield of this SYC is 25%, and the stability of this compound decreases significantly with increasing concentrations of HMS, pH and temperature.
An Epistemic Strategy Logic
Authors: Huang Xiaowei , Meyden Ron Van Der
Published: December 2018

This article presents an extension of temporal epistemic logic with operators that can express quantification over agent strategies. Unlike previous work on alternating temporal epistemic logic, the semantics works with systems whose states explicitly encode the strategy being used by each of the agents. This provides a natural way to express what agents would know were they to be aware of some of the strategies being used by other agents. A number of examples that rely on the ability to express an agent’s knowledge about the strategies being used by other agents are presented to motivate the framework, including reasoning about game-theoretic equilibria, knowledge-based programs, and information-theoretic computer security policies. Relationships to several variants of alternating temporal epistemic logic are discussed. The computational complexity of model checking the logic and several of its fragments are also characterized.
Test-Based Security Certification of Composite Services
Authors: Anisetti Marco , Ardagna Claudio , Damiani Ernesto , Polegri Gianluca
Published: December 2018

The diffusion of service-based and cloud-based systems has created a scenario where software is often made available as services, offered as commodities over corporate networks or the global net. This scenario supports the definition of business processes as composite services, which are implemented via either static or runtime composition of offerings provided by different suppliers. Fast and accurate evaluation of services’ security properties becomes then a fundamental requirement and is nowadays part of the software development process. In this article, we show how the verification of security properties of composite services can be handled by test-based security certification and built to be effective and efficient in dynamic composition scenarios. Our approach builds on existing security certification schemes for monolithic services and extends them towards service compositions. It virtually certifies composite services, starting from certificates awarded to the component services. We describe three heuristic algorithms for generating runtime test-based evidence of the composite service holding the properties. These algorithms are compared with the corresponding exhaustive algorithm to evaluate their quality and performance. We also evaluate the proposed approach in a real-world industrial scenario, which considers ENGpay online payment system of Engineering Ingegneria Informatica S.p.A. The proposed industrial evaluation presents the utility and generality of the proposed approach by showing how certification results can be used as a basis to establish compliance to Payment Card Industry Data Security Standard.
Gloss
Authors: Rajadurai Sumanaruban , Bosboom Jeffrey , Wong Weng-Fai , Amarasinghe Saman
Published: December 2018

An important class of applications computes on long-running or infinite streams of data, often with known fixed data rates. The latter is referred to as
synchronous data flow
~(SDF) streams. These stream applications need to run on clusters or the cloud due to the high performance requirement. Further, they require live reconfiguration and reoptimization for various reasons such as hardware maintenance, elastic computation, or to respond to fluctuations in resources or application workload. However, reconfiguration and reoptimization without downtime while accurately preserving program state in a distributed environment is difficult. In this paper, we introduce Gloss, a suite of compiler and runtime techniques for live reconfiguration of distributed stream programs. Gloss, for the first time, avoids periods of zero throughput during the reconfiguration of both stateless and stateful SDF based stream programs. Furthermore, unlike other systems, Gloss globally reoptimizes and completely recompiles the program during reconfiguration. This permits it to reoptimize the application for entirely new configurations that it may not have encountered before. All these Gloss operations happen in-situ, requiring no extra hardware resources. We show how Gloss allows stream programs to reconfigure and reoptimize with no downtime and minimal overhead, and demonstrate the wider applicability of it via a variety of experiments.
In-Memory Data Parallel Processor
Authors: Fujiki Daichi , Mahlke Scott , Das Reetuparna
Published: December 2018

Recent developments in Non-Volatile Memories (NVMs) have opened up a new horizon for in-memory computing. Despite the significant performance gain offered by computational NVMs, previous works have relied on manual mapping of specialized kernels to the memory arrays, making it infeasible to execute more general workloads. We combat this problem by proposing a programmable in-memory processor architecture and data-parallel programming framework. The efficiency of the proposed in-memory processor comes from two sources: massive parallelism and reduction in data movement. A compact instruction set provides generalized computation capabilities for the memory array. The proposed programming framework seeks to leverage the underlying parallelism in the hardware by merging the concepts of data-flow and vector processing. To facilitate in-memory programming, we develop a compilation framework that takes a TensorFlow input and generates code for our in-memory processor. Our results demonstrate 7.5x speedup over a multi-core CPU server for a set of applications from Parsec and 763x speedup over a server-class GPU for a set of Rodinia benchmarks.
Blasting through the Front-End Bottleneck with Shotgun
Authors: Kumar Rakesh , Grot Boris , Nagarajan Vijay
Published: December 2018

The front-end bottleneck is a well-established problem in server workloads owing to their deep software stacks and large instruction working sets. Despite years of research into effective L1-I and BTB prefetching, state-of-the-art techniques force a trade-off between performance and metadata storage costs. This work introduces Shotgun, a BTB-directed front-end prefetcher powered by a new BTB organization that maintains a logical map of an application's instruction footprint, which enables high-efficacy prefetching at low storage cost. To map active code regions, Shotgun precisely tracks an application's global control flow (e.g., function and trap routine entry points) and summarizes local control flow within each code region. Because the local control flow enjoys high spatial locality, with most functions comprised of a handful of instruction cache blocks, it lends itself to a compact region-based encoding. Meanwhile, the global control flow is naturally captured by the application's unconditional branch working set (calls, returns, traps). Based on these insights, Shotgun devotes the bulk of its BTB capacity to branches responsible for the global control flow and a spatial encoding of their target regions. By effectively capturing a map of the application's instruction footprint in the BTB, Shotgun enables highly effective BTB-directed prefetching. Using a storage budget equivalent to a conventional BTB, Shotgun outperforms the state-of-the-art BTB-directed front-end prefetcher by up to 14% on a set of varied commercial workloads.
Time Dilation and Contraction for Programmable Analog Devices with Jaunt
Authors: Achour Sara , Rinard Martin
Published: December 2018

Programmable analog devices are a powerful new computing substrate that are especially appropriate for performing computationally intensive simulations of neuromorphic and cytomorphic models. Current state of the art techniques for configuring analog devices to simulate dynamical systems do not consider the current and voltage operating ranges of analog device components or the sampling limitations of the digital interface of the device. We present Jaunt, a new solver that scales the values that configure the analog device to ensure the resulting analog computation executes within the operating constraints of the device, preserves the recoverable dynamics of the original simulation, and executes slowly enough to observe these dynamics at the sampled digital outputs. Our results show that, on a set of benchmark biological simulations, 1) unscaled configurations produce incorrect simulations because they violate the operating ranges of the device and 2) Jaunt delivers scaled configurations that respect the operating ranges to produce correct simulations with observable dynamics.
CALOREE
Authors: Mishra Nikita , Imes Connor , Lafferty John D. , Hoffmann Henry
Published: December 2018

Many modern computing systems must provide reliable latency with minimal energy. Two central challenges arise when allocating system resources to meet these conflicting goals: (1) complexity modern hardware exposes diverse resources with complicated interactions and (2) dynamics latency must be maintained despite unpredictable changes in operating environment or input. Machine learning accurately models the latency of complex, interacting resources, but does not address system dynamics; control theory adjusts to dynamic changes, but struggles with complex resource interaction. We therefore propose CALOREE, a resource manager that learns key control parameters to meet latency requirements with minimal energy in complex, dynamic en- vironments. CALOREE breaks resource allocation into two sub-tasks: learning how interacting resources affect speedup, and controlling speedup to meet latency requirements with minimal energy. CALOREE deines a general control system whose parameters are customized by a learning framework while maintaining control-theoretic formal guarantees that the latency goal will be met. We test CALOREE's ability to deliver reliable latency on heterogeneous ARM big.LITTLE architectures in both single and multi-application scenarios. Compared to the best prior learning and control solutions, CALOREE reduces deadline misses by 60% and energy consumption by 13%.
LATR
Authors: Kumar Mohan Kumar , Maass Steffen , Kashyap Sanidhya , Veselý Ján , Yan Zi , Kim Taesoo , Bhattacharjee Abhishek , Krishna Tushar
Published: December 2018

We propose LATR-lazy TLB coherence-a software-based TLB shootdown mechanism that can alleviate the overhead of the synchronous TLB shootdown mechanism in existing operating systems. By handling the TLB coherence in a lazy fashion, LATR can avoid expensive IPIs which are required for delivering a shootdown signal to remote cores, and the performance overhead of associated interrupt handlers. Therefore, virtual memory operations, such as free and page migration operations, can benefit significantly from LATR's mechanism. For example, LATR improves the latency of munmap() by 70.8% on a 2-socket machine, a widely used configuration in modern data centers. Real-world, performance-critical applications such as web servers can also benefit from LATR: without any application-level changes, LATR improves Apache by 59.9% compared to Linux, and by 37.9% compared to ABIS, a highly optimized, state-of-the-art TLB coherence technique.
SPECTR
Authors: Rahmani Amir M. , Donyanavard Bryan , Mück Tiago , Moazzemi Kasra , Jantsch Axel , Mutlu Onur , Dutt Nikil
Published: December 2018

Resource management strategies for many-core systems need to enable sharing of resources such as power, processing cores, and memory bandwidth while coordinating the priority and significance of system- and application-level objectives at runtime in a scalable and robust manner. State-of-the-art approaches use heuristics or machine learning for resource management, but unfortunately lack formalism in providing robustness against unexpected corner cases. While recent efforts deploy classical control-theoretic approaches with some guarantees and formalism, they lack scalability and autonomy to meet changing runtime goals. We present SPECTR, a new resource management approach for many-core systems that leverages formal supervisory control theory (SCT) to combine the strengths of classical control theory with state-of-the-art heuristic approaches to efficiently meet changing runtime goals. SPECTR is a scalable and robust control architecture and a systematic design flow for hierarchical control of many-core systems. SPECTR leverages SCT techniques such as gain scheduling to allow autonomy for individual controllers. It facilitates automatic synthesis of the high-level supervisory controller and its property verification. We implement SPECTR on an Exynos platform containing ARM»s big.LITTLE-based heterogeneous multi-processor (HMP) and demonstrate that SPECTR»s use of SCT is key to managing multiple interacting resources (e.g., chip power and processing cores) in the presence of competing objectives (e.g., satisfying QoS vs. power capping). The principles of SPECTR are easily applicable to any resource type and objective as long as the management problem can be modeled using dynamical systems theory (e.g., difference equations), discrete-event dynamic systems, or fuzzy dynamics.
Watching for Software Inefficiencies with Witch
Authors: Wen Shasha , Liu Xu , Byrne John , Chabbi Milind
Published: December 2018

Inefficiencies abound in complex, layered software. A variety of inefficiencies show up as wasteful memory operations. Many existing tools instrument every load and store instruction to monitor memory, which significantly slows execution and consumes enormously extra memory. Our lightweight framework, Witch, samples consecutive accesses to the same memory location by exploiting two ubiquitous hardware features: the performance monitoring units (PMU) and debug registers. Witch performs no instrumentation. Hence, witchcraft---tools built atop Witch---can detect a variety of software inefficiencies while introducing negligible slowdown and insignificant memory consumption and yet maintaining accuracy comparable to exhaustive instrumentation tools. Witch allowed us to scale our analysis to a large number of code bases. Guided by witchcraft, we detected several performance problems in important code bases; eliminating these inefficiencies resulted in significant speedups.
Putting in all the stops: execution control for JavaScript
Authors: Baxter Samuel , Nigam Rachit , Politz Joe Gibbs , Krishnamurthi Shriram , Guha Arjun
Published: December 2018

Scores of compilers produce JavaScript, enabling programmers to use many languages on the Web, reuse existing code, and even use Web IDEs. Unfortunately, most compilers inherit the browser's compromised execution model, so long-running programs freeze the browser tab, infinite loops crash IDEs, and so on. The few compilers that avoid these problems suffer poor performance and are difficult to engineer.

This paper presents Stopify, a source-to-source compiler that extends JavaScript with debugging abstractions and blocking operations, and easily integrates with existing compilers. We apply Stopify to ten programming languages and develop a Web IDE that supports stopping, single-stepping, breakpointing, and long-running computations. For nine languages, Stopify requires no or trivial compiler changes. For eight, our IDE is the first that provides these features. Two of our subject languages have compilers with similar features. Stopify's performance is competitive with these compilers and it makes them dramatically simpler.

Stopify's abstractions rely on first-class continuations, which it provides by compiling JavaScript to JavaScript. We also identify sub-languages of JavaScript that compilers implicitly use, and exploit these to improve performance. Finally, Stopify needs to repeatedly interrupt and resume program execution. We use a sampling-based technique to estimate program speed that outperforms other systems.
MixT: a language for mixing consistency in geodistributed transactions
Authors: Milano Mae , Myers Andrew C.
Published: December 2018

Programming concurrent, distributed systems is hard—especially when these systems mutate shared, persistent state replicated at geographic scale. To enable high availability and scalability, a new class of weakly consistent data stores has become popular. However, some data needs strong consistency. To manipulate both weakly and strongly consistent data in a single transaction, we introduce a new abstraction: mixed-consistency transactions, embodied in a new embedded language, MixT. Programmers explicitly associate consistency models with remote storage sites; each atomic, isolated transaction can access a mixture of data with different consistency models. Compile-time information-flow checking, applied to consistency models, ensures that these models are mixed safely and enables the compiler to automatically partition transactions. New run-time mechanisms ensure that consistency models can also be mixed safely, even when the data used by a transaction resides on separate, mutually unaware stores. Performance measurements show that despite their stronger guarantees, mixed-consistency transactions retain much of the speed of weak consistency, significantly outperforming traditional serializable transactions.
Certified concurrent abstraction layers
Authors: Gu Ronghui , Shao Zhong , Kim Jieung , Wu Xiongnan (Newman) , Koenig Jérémie , Sjöberg Vilhelm , Chen Hao , Costanzo David , Ramananandro Tahina
Published: December 2018

Concurrent abstraction layers are ubiquitous in modern computer systems because of the pervasiveness of multithreaded programming and multicore hardware. Abstraction layers are used to hide the implementation details (e.g., fine-grained synchronization) and reduce the complex dependencies among components at different levels of abstraction. Despite their obvious importance, concurrent abstraction layers have not been treated formally. This severely limits the applicability of layer-based techniques and makes it difficult to scale verification across multiple concurrent layers.

In this paper, we present CCAL---a fully mechanized programming toolkit developed under the CertiKOS project---for specifying, composing, compiling, and linking certified concurrent abstraction layers. CCAL consists of three technical novelties: a new game-theoretical, strategy-based compositional semantic model for concurrency (and its associated program verifiers), a set of formal linking theorems for composing multithreaded and multicore concurrent layers, and a new CompCertX compiler that supports certified thread-safe compilation and linking. The CCAL toolkit is implemented in Coq and supports layered concurrent programming in both C and assembly. It has been successfully applied to build a fully certified concurrent OS kernel with fine-grained locking.
Guarded impredicative polymorphism
Authors: Serrano Alejandro , Hage Jurriaan , Vytiniotis Dimitrios , Peyton Jones Simon
Published: December 2018

The design space for type systems that support impredicative instantiation is extremely complicated. One needs to strike a balance between expressiveness, simplicity for both the end programmer and the type system implementor, and how easily the system can be integrated with other advanced type system concepts. In this paper, we propose a new point in the design space, which we call guarded impredicativity. Its key idea is that impredicative instantiation in an application is allowed for type variables that occur under a type constructor. The resulting type system has a clean declarative specification — making it easy for programmers to predict what will type and what will not —, allows for a smooth integration with GHC’s OutsideIn(X) constraint solving framework, while giving up very little in terms of expressiveness compared to systems like HMF, HML, FPH and MLF. We give a sound and complete inference algorithm, and prove a principal type property for our system.
On-stack replacement, distilled
Authors: D'Elia Daniele Cono , Demetrescu Camil
Published: December 2018

On-stack replacement (OSR) is essential technology for adaptive optimization, allowing changes to code actively executing in a managed runtime. The engineering aspects of OSR are well-known among VM architects, with several implementations available to date. However, OSR is yet to be explored as a general means to transfer execution between related program versions, which can pave the road to unprecedented applications that stretch beyond VMs. We aim at filling this gap with a constructive and provably correct OSR framework, allowing a class of general-purpose transformation functions to yield a special-purpose replacement. We describe and evaluate an implementation of our technique in LLVM. As a novel application of OSR, we present a feasibility study on debugging of optimized code, showing how our techniques can be used to fix variables holding incorrect values at breakpoints due to optimizations.
Finding root causes of floating point error
Authors: Sanchez-Stern Alex , Panchekha Pavel , Lerner Sorin , Tatlock Zachary
Published: December 2018

Floating-point arithmetic plays a central role in science, engineering, and finance by enabling developers to approximate real arithmetic. To address numerical issues in large floating-point applications, developers must identify root causes, which is difficult because floating-point errors are generally non-local, non-compositional, and non-uniform.

This paper presents Herbgrind, a tool to help developers identify and address root causes in numerical code written in low-level languages like C/C++ and Fortran. Herbgrind dynamically tracks dependencies between operations and program outputs to avoid false positives and abstracts erroneous computations to simplified program fragments whose improvement can reduce output error. We perform several case studies applying Herbgrind to large, expert-crafted numerical programs and show that it scales to applications spanning hundreds of thousands of lines, correctly handling the low-level details of modern floating point hardware and mathematical libraries and tracking error across function boundaries and through the heap.
Static serializability analysis for causal consistency
Authors: Brutschy Lucas , Dimitrov Dimitar , Müller Peter , Vechev Martin
Published: December 2018

Many distributed databases provide only weak consistency guarantees to reduce synchronization overhead and remain available under network partitions. However, this leads to behaviors not possible under stronger guarantees. Such behaviors can easily defy programmer intuition and lead to errors that are notoriously hard to detect.

In this paper, we propose a static analysis for detecting non-serializable behaviors of applications running on top of causally-consistent databases. Our technique is based on a novel, local serializability criterion and combines a generalization of graph-based techniques from the database literature with another, complementary analysis technique that encodes our serializability criterion into first-order logic formulas to be checked by an SMT solver. This analysis is more expensive yet more precise and produces concrete counter-examples.

We implemented our methods and evaluated them on a number of applications from two different domains: cloud-backed mobile applications and clients of a distributed database. Our experiments demonstrate that our analysis is able to detect harmful serializability violations while producing only a small number of false alarms.
A data-driven CHC solver
Authors: Zhu He , Magill Stephen , Jagannathan Suresh
Published: December 2018

We present a data-driven technique to solve Constrained Horn Clauses (CHCs) that encode verification conditions of programs containing unconstrained loops and recursions. Our CHC solver neither constrains the search space from which a predicate's components are inferred (e.g., by constraining the number of variables or the values of coefficients used to specify an invariant), nor fixes the shape of the predicate itself (e.g., by bounding the number and kind of logical connectives). Instead, our approach is based on a novel machine learning-inspired tool chain that synthesizes CHC solutions in terms of arbitrary Boolean combinations of unrestricted atomic predicates. A CEGAR-based verification loop inside the solver progressively samples representative positive and negative data from recursive CHCs, which is fed to the machine learning tool chain. Our solver is implemented as an LLVM pass in the SeaHorn verification framework and has been used to successfully verify a large number of nontrivial and challenging C programs from the literature and well-known benchmark suites (e.g., SV-COMP).
CUBA: interprocedural Context-UnBounded Analysis of concurrent programs
Authors: Liu Peizun , Wahl Thomas
Published: December 2018

A classical result by Ramalingam about synchronization-sensitive interprocedural program analysis implies that reachability for concurrent threads running recursive procedures is undecidable. A technique proposed by Qadeer and Rehof, to bound the number of context switches allowed between the threads, leads to an incomplete solution that is, however, believed to catch “most bugs” in practice. The question whether the technique can also prove the absence of bugs at least in some cases has remained largely open.

In this paper we introduce a broad verification methodology for resource-parameterized programs that observes how changes to the resource parameter affect the behavior of the program. Applied to the
context-unbounded analysis problem
(CUBA), the methodology results in partial verification techniques for procedural concurrent programs. Our solutions may not terminate, but are able to both refute and prove context-unbounded safety for concurrent recursive threads. We demonstrate the effectiveness of our method using a variety of examples, the safe of which cannot be proved safe by earlier, context-bounded methods.