bluuebunny/crossref_metadata_2025 huggingface dataset:
A unique predator in a unique ecosystem: modelling the apex predator within a Late Cretaceous crocodyliform‐dominated fauna from Brazil
Authors: Montefeltro Felipe C. , Lautenschlager Stephan , Godoy Pedro L. , Ferreira Gabriel S. , Butler Richard J.
Published: April 2020

Theropod dinosaurs were relatively scarce in the Late Cretaceous ecosystems of southeast Brazil. Instead, hypercarnivorous crocodyliforms known as baurusuchids were abundant and probably occupied the ecological role of apex predators. Baurusuchids exhibited a series of morphological adaptations hypothesized to be associated with this ecological role, but quantitative biomechanical analyses of their morphology have so far been lacking. Here, we employ a biomechanical modelling approach, applying finite element analysis (FEA) to models of the skull and mandibles of a baurusuchid specimen. This allows us to characterize the craniomandibular apparatus of baurusuchids, as well as to compare the functional morphology of the group with that of other archosaurian carnivores, such as theropods and crocodylians. Our results support the ecological role of baurusuchids as specialized apex predators in the continental Late Cretaceous ecosystems of South America. With a relatively weak bite force (~600 N), the predation strategies of baurusuchids likely relied on other morphological specializations, such as ziphodont dentition and strong cervical musculature. Comparative assessments of the stress distribution and magnitude of scaled models of other predators (the theropod Allosaurus fragilis and the living crocodylian Alligator mississippiensis) consistently show different responses to loadings under the same functional scenarios, suggesting distinct predatory behaviors for these animals. The unique selective pressures in the arid to semi‐arid Late Cretaceous ecosystems of southeast Brazil, which were dominated by crocodyliforms, possibly drove the emergence and evolution of the biomechanical features seen in baurusuchids, which are distinct from those previously reported for other predatory taxa.
Models and frameworks that enable nurses to develop their public health practice—A scoping study
Authors: Ezhova Ivanka , Sayer Lynn , Newland Rita , Davis Nicola , McLetchie‐Holder Shelley , Burrows Patricia , Middleton Laura , Malone Mary Ellen
Published: April 2020

Aims and objectives

This scoping review commissioned by the Public Health England, WHO collaborating Centre, aimed to explore the models and frameworks which enable nurses to develop their public health practice and deliver public health interventions to individuals, families and communities.

Background

There is a plethora of literature regarding the role, activities and scope of practice undertaken by public health nurses across the world. However, only two reviews have explored the models and frameworks used for public health nursing practice.

Design

The study drew upon an established framework with a narrative review drawing upon five methodological steps.

Methods

A search of databases, Medline, PsycINFO, Embase, CINHAL and British Nursing Index, was undertaken. The search took place between April 2018 and June 2018 retrieving 9,513 peer‐reviewed articles published from 2008.

Results

Ninety‐five studies were retrieved and analysed thematically. From an initial review of literature, two themes were identified: public health models used in practice and models used in public health education. Within the first theme, three subthemes were emerged: Characteristics of the interventions; Characteristics of the public health nurse; and Lack of measurable health benefits. Within the second theme, three subthemes were identified: Faculty and Students Working Together; The Experiential Academic Approach, and What works in Educating Nurses for Public Health.

Conclusion

The review identified that many models and frameworks are used in practice. However, within public health practice there is a limited evidence base and it fails to demonstrate that the frameworks and models developed for practice result in measurable health benefits on an individual or population level. However, within education innovative models were apparent with collaborative partnerships enabling preregistration nursing students to develop public health nursing competencies.

Relevance to clinical practice

Innovative approaches to education of preregistration nursing students could point the way forward for the delivery of public health nursing practice.
Diagnostic markers of allergic bronchopulmonary aspergillosis in patients with severe asthma
Authors: Kozlova Yana , Frolova Ekaterina , Uchevatkina Aleksandra , Filippova Larisa , Aak Oleg , Burygina Ekaterina , Taraskina Anastasiya , Vasilyeva Natalia , Klimko Nikolay
Published: April 2020

Introduction

Allergic bronchopulmonary aspergillosis (ABPA) is a lung disease in patients with asthma or cystic fibrosis (CF) caused by chronic allergic inflammation to Aspergillus spp. antigens. The role of different immunological mediators in the formation of chronic allergic inflammation in patients with ABPA is not sufficiently explored.

Objectives

This study aimed to investigate serum levels of thymic stromal lymphopoietin (TSLP), thymus and activated chemokine (TARC) as well as IL‐8 in patients with ABPA, and to evaluate their diagnostic and monitoring value in the disease.

Patients/methods

Prospective study included 21 patients with ABPA, 25 patients with severe asthma with fungal sensitisation (SAFS), 37 patients with severe asthma without fungal sensitisation (SAwFS), and 16 healthy people. In patients with ABPA, the serum levels of biomarkers were determined at baseline and after 12 weeks of itraconazole therapy. Serum levels of total IgE, Aspergillus‐fumigatus‐specific IgE, TSLP, TARC, IL‐8 were analysed by enzyme‐linked immunosorbent assay.

Results

In patients with ABPA we established significantly higher serum levels of TARC, IL‐8, total IgE, Aspergillus‐fumigatus‐specific IgE and peripheral blood eosinophil counts, compared to patients with SAwFS. There were no differences in TSLP levels between the examined groups of patients. Serum TARC levels were positively correlated to serum total IgE levels, A fumigatus‐specific IgE levels and peripheral blood eosinophil counts and also negatively correlated to lung function (FEV1). Longitudinally, serum levels TARC, total IgE and peripheral blood eosinophil counts significant decreased after treatment of ABPA.

Conclusion

Thymus and activated chemokine is a useful test in diagnosing and monitoring response to the antifungal treatment of patients with ABPA.
An operational definition of the biome for global change research
Authors: Conradi Timo , Slingsby Jasper A. , Midgley Guy F. , Nottebrock Henning , Schweiger Andreas H. , Higgins Steven I.
Published: April 2020

Biomes are constructs for organising knowledge on the structure and functioning of the world’s ecosystems, and serve as useful units for monitoring how the biosphere responds to anthropogenic drivers, including climate change. The current practice of delimiting biomes relies on expert knowledge. Recent studies have questioned the value of such biome maps for comparative ecology and global‐change research, partly due to their subjective origin. Here we propose a flexible method for developing biome maps objectively. The method uses range modelling of several thousands of plant species to reveal spatial attractors for different growth‐form assemblages that define biomes. The workflow is illustrated using distribution data from 23 500 African plant species. In an example application, we create a biome map for Africa and use the fitted species models to project biome shifts. In a second example, we map gradients of growth‐form suitability that can be used to identify sites for comparative ecology. This method provides a flexible framework that (1) allows a range of biome types to be defined according to user needs and (2) enables projections of biome changes that emerge purely from the individualistic responses of plant species to environmental changes.
Ventricular arrhythmia suppression with ivabradine in a patient with catecholaminergic polymorphic ventricular tachycardia refractory to nadolol, flecainide, and sympathectomy
Authors: Kohli Utkarsh , Aziz Zaid , Beaser Andrew D. , Nayak Hemal M.
Published: April 2020

Conventional treatment strategies for catecholaminergic polymorphic ventricular tachycardia (CPVT) include avoidance of strenuous exercise and competitive sports, drugs such as ß‐blockers and flecainide and, cervical sympathectomy. An implantable cardioverter‐defibrillator (ICD) has been utilized if the response to these strategies is inadequate; however, ICD use in CPVT patients, in addition to usual complications, is associated with an increased risk of life‐threatening electrical storm. Ivabradine is a selective inhibitor of hyperpolarization‐activated cyclic nucleotide‐gated potassium channel 4 generated funny current (If), which has been shown to be efficacious in suppression of inappropriate sinus tachycardia, junctional tachycardia, atrial tachycardia, and ventricular ectopy in humans. We report an 18‐year‐old male with a severe CPVT phenotype refractory to flecainide, nadolol, and sympathectomy who exhibited suppression of ventricular arrhythmias after initiation of ivabradine. These findings are of importance as ivabradine could be an important add‐on therapy in CPVT patients who are drug refractory or are unable to continue conventional therapies at the recommended doses.
Shaping our personal past: Assessing the phenomenology of autobiographical memory and its association with object and spatial imagery
Authors: Vannucci Manila , Chiorri Carlo , Marchetti Igor
Published: April 2020

A new instrument has been developed that allows a comprehensive assessment of the relevant dimensions of the phenomenology of autobiographical memories (Assessment of the Phenomenology of Autobiographical Memory, APAM), and their association with visual object and spatial imagery has been examined. An initial version of APAM consisting of 30 items (the first 28 measured on a seven‐point Likert‐type scale) was developed and administered to a sample of 138 undergraduates. To test whether each item consistently measured the same dimension across different memories, all questions were rated for 12 cues. Results showed that 25 Likert‐type items possessed adequate levels of internal consistency and unidimensionality across cues. We also found that higher levels of visual object imagery were associated with more sensory details and recollective qualities of memory, and with stronger experience of sensory and emotional reliving. The theoretical and practical usefulness of APAM as well as the relevance of visual object imagery in the phenomenology of autobiographical memory are discussed.
Muscle‐tendon morphology and function following long‐term exposure to repeated and strenuous mechanical loading
Authors: Bissas Athanassios , Havenetidis Konstantinos , Walker Josh , Hanley Brian , Nicholson Gareth , Metaxas Thomas , Christoulas Kosmas , Cronin Neil J.
Published: April 2020

We mapped structural and functional characteristics of muscle‐tendon units in a population exposed to very long‐term routine overloading. Twenty‐eight military academy cadets (age = 21.00 ± 1.1 years; height = 176.1 ± 4.8 cm; mass = 73.8 ± 7.0 kg) exposed for over 24 months to repetitive overloading were profiled via ultrasonography with a senior subgroup of them (n = 11; age = 21.4 ± 1.0 years; height = 176.5 ± 4.8 cm; mass = 71.4 ± 6.6 kg) also tested while walking and marching on a treadmill. A group of eleven ethnicity‐ and age‐matched civilians (age = 21.6 ± 0.7 years; height = 176.8 ± 4.3 cm; mass = 74.6 ± 5.6 kg) was also profiled and tested. Cadets and civilians exhibited similar morphology (muscle and tendon thickness and cross‐sectional area, pennation angle, fascicle length) in 26 out of 29 sites including the Achilles tendon. However, patellar tendon thickness along the entire tendon was greater (P < .05) by a mean of 16% for the senior cadets compared with civilians. Dynamically, cadets showed significantly smaller ranges of fascicle length change and lower shortening velocity in medial gastrocnemius during walking (44.0% and 47.6%, P < .05‐.01) and marching (27.5% and 34.3%, P < .05‐.01) than civilians. Furthermore, cadets showed lower normalized soleus electrical activity during walking (22.7%, P < .05) and marching (27.0%, P < .05). Therefore, 24‐36 months of continuous overloading, primarily occurring under aerobic conditions, leads to more efficient neural and mechanical behavior in the triceps surae complex, without any major macroscopic alterations in key anatomical structures.
Modeling node heterogeneity in latent space models for multidimensional networks
Authors: D'Angelo Silvia , Alfò Marco , Brendan Murphy Thomas
Published: April 2020

Multidimensional network data can have different levels of complexity, as nodes may be characterized by heterogeneous individual‐specific features, which may vary across the networks. This article introduces a class of models for multidimensional network data, where different levels of heterogeneity within and between networks can be considered. The proposed framework is developed in the family of latent space models, and it aims to distinguish symmetric relations between the nodes and node‐specific features. Model parameters are estimated via a Markov Chain Monte Carlo algorithm. Simulated data and an application to a real example, on fruits import/export data, are used to illustrate and comment on the performance of the proposed models.
Sarcomas—A barren immunological wasteland or field of opportunity for immunotherapy?
Authors: Atherton Matthew J. , Lenz Jennifer A. , Mason Nicola J.
Published: April 2020

Key advances in our understanding of immunobiology and the immunosuppressive mechanisms of the tumour microenvironment have led to significant breakthroughs in manipulating the immune system to successfully treat cancer. Remarkable therapeutic responses have occurred with tumours that carry a high mutational burden. In these cases, pre‐existing tumour‐specific T cells can be rejuvenated via checkpoint inhibition to eliminate tumours. Furthermore, durable remissions have been achieved in haematological malignancies following adoptive transfer of T cells that specifically target cell surface proteins where expression is restricted to the malignancy's cell of origin. Soft tissue sarcomas and bone sarcomas have a paucity of non‐synonymous somatic mutations and do not commonly express known, targetable, tumour‐specific antigens. Historically, soft tissue sarcomas have been considered immunologically ‘cold’ and as such, unlikely candidates for immune therapy. Here, we review the immune landscape of canine and feline sarcomas and the immunotherapeutic strategies that have been employed in veterinary clinical trials to improve patient outcome. We also provide insight into immunotherapeutic approaches being used to treat human sarcomas. Together, current data indicates that, rather than a barren immunological wasteland, sarcomas represent a field of opportunities for immunotherapies. Furthermore, we and others would suggest that strategic combinations of immunotherapeutic approaches may hold promise for more effective treatments for high grade soft tissue sarcomas and bone sarcomas.
Ultrasonographic assessment of male anterior urethra. Description of the technique of examination and presentation of major pathologies.
Authors: Krukowski Jakub , Frankiewicz Mikołaj , Kałużny Adam , Matuszewski Marcin
Published: April 2020

During the last years the role of sonourethrography (SUG) in the assessment of anterior male urethra pathologies, has significantly increased. The investigation is easily performed, not time consuming and should be considered the imaging technique of choice for preliminary diagnosis, without exposing the patient to X-rays. In this paper we present the technique of examination and the most common pathologies in which SUG is indicated.
Layer-resolved ultrafast extreme ultraviolet measurement of hole transport in a Ni-TiO
2
-Si photoanode
Authors: Cushing Scott K. , Porter Ilana J. , de Roulet Bethany R. , Lee Angela , Marsh Brett M. , Szoke Szilard , Vaida Mihai E. , Leone Stephen R.
Published: April 2020

Ultrafast charge carrier migration through all the layers of a nanojunction is observed and quantified.
“Skin-like” fabric for personal moisture management
Authors: Lao L. , Shou D. , Wu Y. S. , Fan J. T.
Published: April 2020

A super breathable skin-like fabric with artificial sweating glands to excrete fluid droplets and repel external liquids.
Massive generation of metastable bulk nanobubbles in water by external electric fields
Authors: Ghaani Mohammad Reza , Kusalik Peter G. , English Niall J.
Published: April 2020

We describe a groundbreaking approach to generate long-lived bulk nanobubbles in water by external electric fields.
A metal-free blue chromophore derived from plant pigments
Authors: Freitas-Dörr B. C. , Machado C. O. , Pinheiro A. C. , Fernandes A. B. , Dörr F. A. , Pinto E. , Lopes-Ferreira M. , Abdellah M. , Sá J. , Russo L. C. , Forti F. L. , Gonçalves L. C. P. , Bastos E. L.
Published: April 2020

The red pigments of beets are used to produce BeetBlue, a biocompatible blue dye.
Co-opted Cellular Sac1 Lipid Phosphatase and PI(4)P Phosphoinositide Are Key Host Factors during the Biogenesis of the Tombusvirus Replication Compartment
Authors: Sasvari Zsuzsanna , Lin Wenwu , Inaba Jun-Ichi , Xu Kai , Kovalev Nikolay , Nagy Peter D.
Published: April 2020

Replication of positive-strand RNA viruses depends on recruitment of host components into viral replication compartments or organelles. Using TBSV, we uncovered the critical roles of Sac1 PI(4)P phosphatase and its substrate, PI(4)P phosphoinositide, in promoting viral replication. Both Sac1 and PI(4)P are recruited to the site of viral replication to facilitate the assembly of the viral replicase complexes, which perform viral RNA replication. We found that Sac1 affects the recruitment of other host factors and enrichment of phosphatidylethanolamine and sterol lipids within the subverted host membranes to promote optimal viral replication. In summary, this work demonstrates the novel functions of Sac1 and PI(4)P in TBSV replication in the model host yeast and in plants.
The Aedes aegypti Domino Ortholog p400 Regulates Antiviral Exogenous Small Interfering RNA Pathway Activity and
ago-2
Expression
Authors: McFarlane Melanie , Almire Floriane , Kean Joy , Donald Claire L. , McDonald Alma , Wee Bryan , Lauréti Mathilde , Varjak Margus , Terry Sandra , Vazeille Marie , Gestuveo Rommel J. , Dietrich Isabelle , Loney Colin , Failloux Anna-Bella , Schnettler Esther , Pondeville Emilie , Kohl Alain
Published: April 2020

Female
Aedes aegypti
mosquitoes are vectors of human-infecting arthropod-borne viruses (arboviruses). In recent decades, the incidence of arthropod-borne viral infections has grown dramatically. Vector competence is influenced by many factors, including the mosquito’s antiviral defenses. The exogenous small interfering RNA (siRNA) pathway is a major antiviral response restricting arboviruses in mosquitoes. While the roles of the effectors of this pathway, Argonaute-2 and Dicer-2 are well characterized, nothing is known about its regulation in mosquitoes. In this study, we demonstrate that
A. aegypti
p400, whose ortholog Domino in
Drosophila melanogaster
is a chromatin-remodeling ATPase member of the Tip60 complex, regulates siRNA pathway activity and controls
ago-2
expression levels. In addition, we found p400 to have antiviral activity against different arboviruses. Therefore, our study provides new insights into the regulation of the antiviral response in
A. aegypti
mosquitoes.
Sedimentological characteristics and aeolian architecture of a plausible intermountain erg system in Southeast China during the Late Cretaceous
Authors: Cao Shuo , Zhang Laiming , Wang Chengshan , Ma Jing , Tan Jie , Zhang Zhihui
Published: April 2020

Along with intensification of global warming, severe desertification has already impaired human sustainable development. In a near-future greenhouse world, the total area of desert will increase, and new types of desert may emerge. During the “greenhouse” Cretaceous, conventional large paleo-ergs developed in broad topographic basins, and many possible ergs developed in small-scale intermountain basins, which are unusual in near-modern times and less studied. A comprehensive study of their sedimentary architecture and mechanisms would refine our interpretation of desertification in a near-future “greenhouse” world. The Xinjiang Basin is a typical small-scale intermountain basin in Southeast China that formed >300 m of successive aeolian deposits during the early Late Cretaceous. In this study, we applied detailed facies and architecture analyses to the Tangbian Formation (K2t) in 16 outcrops throughout the Xinjiang Basin and reconstructed a three-dimensional sedimentary model for the intermountain ergs. We confirmed that the Tangbian Formation formed in a typical intermountain paleo-erg and summarized in detail the differences in sedimentary architecture between intermountain ergs and broad topographic ergs. We noticed that the “greenhouse” state during the Late Cretaceous seems to have been suitable for the development of ergs in intermountain basins due to the hot, arid climate conditions and penetrating winds with sufficient transport capacity. Therefore, we suggest that in addition to the ongoing expansion of broad topographic ergs, the emergence and development of intermountain ergs in a near-future “greenhouse” world would also contribute to global desert expansion and massive desertification.
Accurate estimation of conservation unit contribution to coho salmon mixed-stock fisheries in British Columbia, Canada, using direct DNA sequencing for single nucleotide polymorphisms
Authors: Beacham Terry D. , Wallace Colin , Jonsen Kim , McIntosh Brenda , Candy John R. , Rondeau Eric B. , Moore Jean-Sébastien , Bernatchez Louis , Withler Ruth E.
Published: April 2020

Determination of population structure and stock identification is a ubiquitous problem in fisheries assessment and management. Pacific salmon fishery management regimes are evolving to require higher resolution of stock composition on increasingly smaller reporting units. For coho salmon (Oncorhynchus kisutch), a stock identification baseline composed of some 57 982 individuals from 332 populations ranging from southeast Russia to California was employed for genetic stock identification (GSI). GSI analysis based upon variation at up to 480 single nucleotide polymorphisms (SNPs) was demonstrated to provide accurate estimates of stock composition for 37 conservation units (CU) in British Columbia, 13 reporting groups in the United States, and one reporting group in Russia. In many instances, accurate population-specific estimates of stock composition within a CU were possible in fishery samples, as well as identifying individuals to some specific populations. A genetics-based assessment system provides an opportunity for conservation-based management of Canadian coho salmon.
Partitioning and solving large-scale tactical harvest scheduling problems for industrial plantation forests
Authors: Bellavenutte Pedro , Chung Woodam , Diaz-Balteiro Luis
Published: April 2020

Spatially explicit, tactical forest planning is a necessary but challenging task in the management of plantation forests. It involves harvest scheduling and planning for road access and log transportation over time and space. This combinatorial problem can be formulated into the fixed-charge transportation problem (FCTP), in which the sum of fixed and variable costs is minimized while meeting harvest volume requirements and allowing necessary road maintenance and log hauling activities. The problem can be solved using general optimization methods such as mixed-integer linear programming (MILP), but the computational efficiency of the MILP-based approach quickly drops as the size and complexity of the problem increases. We developed a new optimization procedure that partitions the large planning problem into smaller subproblems. We applied a hybrid optimization approach using both MILP and heuristic rules to efficiently solve the large FCTP that otherwise may not be solvable using traditional methods. We applied our approach to an industrial plantation forest in Brazil. Our applications demonstrate the performance of the new optimization procedure and the benefit of solving large forest planning problems that integrate harvest scheduling with road access and transportation.
Driving and managing architectural decisions with aspects
Authors: Garcia Alessandro , Batista Thais , Rashid Awais , Sant'Anna Claudio
Published: April 2020

Software architects face decisions every day which have a broadly-scoped impact on the software architecture. These decisions are the core of the architecting process as they typically have implications in a multitude of architectural elements and views. Without an explicit representation and management of those crucial choices, architects cannot properly communicate and reason about them and their crosscutting effects. The result is a number of architectural breakdowns, such as decreased evolvability, time-consuming trade-off analysis, and unmanageable traceability. Aspects are a natural way to capture widely-scoped architectural decisions and promote software architectures with superior modularity.
An assessment of structured analysis and structured design
Authors: Richter Charles A.
Published: April 2020

This paper is a personal assessment of the Structured Analysis and Structured Design methods of Tom DeMarco [1] and Edward Yourdon and Larry Constantine [2]. The assessment is a reflection of my experience using Structured Analysis and Structured Design on a multi-person project during the late 1970s.Structured Analysis and Structured Design are of interest to this workshop for three reasons. First, they are well-documented instances of
methods
, one of the topics of the workshop. Second, they are in use today, thereby providing us with one view of the current state of practice. Finally, in their strengths and weaknesses, they may be representative of a class of current methods.
A Critical Reading of "The Right Tool for the Right Job"
Authors: Taylor Lee
Published: April 2020

Doing a critical reading of a paper presented at a conference you did not attend is a somewhat disembodied experience. Writing about your impressions doesn't help matters: "I wonder if they cleared that up at the conference?" I mutter to myself. Or, "I'm sure they expanded on that in Ottawa."
Tracing garbage collection on highly parallel platforms
Authors: Barabash Katherine , Petrank Erez
Published: April 2020

The pervasiveness of multiprocessor and multicore hardware and the rising level of available parallelism are radically changing the computing landscape. Can software deal with tomorrow's potential higher parallelism? In this paper we study this issue from the garbage collection perspective. In particular, we investigate the scalability of parallel heap tracing, which stands at the core of the garbage collection activity. Heap shapes can be sequential in nature, and prevent the collector from scaling the trace. We start by proposing the idealized trace utilization as a scalability measure for evaluating the scalability of a given heap shape. We then examine standard Java benchmarks and evaluate the existence of non-scalable object-graph shapes in their execution. Next, we propose and implement a prototype of garbage collection techniques that attempt to ameliorate the object-graph shape problem. Finally, we measure and report their efficacy.
Concurrent, parallel, real-time garbage-collection
Authors: Siebert Fridtjof
Published: April 2020

With the current developments in CPU implementations, it becomes obvious that ever more parallel multicore systems will be used even in embedded controllers that require real-time guarantees. When garbage collection is used in these systems, parallel and concurrent garbage collection brings important performance advantages in the average case. In a real-time system, however, guarantees on the GC's performance in the worst case are required.

This paper explains how the single-CPU real-time GC of the Java implementation JamaicaVM was changed to make it a hard real-time garbage collector that is parallel and concurrent. Parallel means that an arbitrary number of CPUs may perform GC work in parallel, while concurrent means that the GC work can be performed concurrently to the application code without pre-empting the application. In addition, the single units of work that this garbage collector has to perform are very small and uniform and the total amount of GC work is bounded by a function of the heap size, such that it becomes possible for any application that has a bounded amount of reachable memory to run the GC work such that sufficient GC progress can be ensured for the application never to run out of heap space.
Memory, an elusive abstraction
Authors: Sewell Peter
Published: April 2020

Multiprocessors are now ubiquitous. They provide an abstraction of shared memory, accessible by concurrently executing threads, which supports a wide range of software. However, exactly what this key abstraction is -- what the hardware designers implement, and what programmers can depend on -- is surprisingly elusive. In 1979, when articulating the notion of sequential consistency (SC), Lamport wrote "For some applications, achieving sequential consistency may not be worth the price of slowing down the processors." [7], and indeed most major multiprocessor families, including Alpha, ARM, Itanium, Power, Sparc, and x86, do not provide the abstraction of SC memory. Internally, they incorporate a range of sophisticated optimisations which have various programmer-visible effects. For some (such as Sparc) these effects are captured in a well-defined relaxed memory model, making it possible (if challenging) to reason with confidence about the behaviour of concurrent programs. For others, however, it has been very unclear what a reasonable model is, despite extensive research over the last three decades. In this talk, I will reflect on the experience of my colleagues and I in trying to establish usable models for x86 multiprocessors, where it appears that our x86-TSO model suffices for common-case code [1-4], and for Power and ARM multiprocessors, where we have models that capture some but not all aspects of their behaviour [5,6]. The underlying causes of these difficulties are complex, including:

The programmer-observable relaxed-memory behaviour of a multiprocessor is a whole-system property that arises from the interaction between many complex aspects of the processor implementation: speculative execution, store buffering, cache protocol, and so forth.

Programs are executed (and tested) on specific multiprocessor implementations, but processor vendors attempt to document loose specifications to cover a range of possible (past and future) implementations

Multiprocessor implementation details are typically confidential and may change radically from one implementation to another

Vendor specifications suffer from the tension between the need for loose specification, to preserve freedom for such changes, and the need for tight specification, to give strong properties to properties

All too often, loose specification has been achieved by vague specification, using informal prose. When it comes to subtle concurrent properties this is almost inevitably ambiguous; it also makes it impossible (even in principle) to test conformance between a processor implementation and such a specification, let alone to verify such a correspondence or to reason about concurrent programs.
Parasol and GreenSwitch
Authors: Goiri Íñigo , Katsak William , Le Kien , Nguyen Thu D. , Bianchini Ricardo
Published: April 2020

Several companies have recently announced plans to build "green" datacenters, i.e. datacenters partially or completely powered by renewable energy. These datacenters will either generate their own renewable energy or draw it directly from an existing nearby plant. Besides reducing carbon footprints, renewable energy can potentially reduce energy costs, reduce peak power costs, or both. However, certain renewable fuels are intermittent, which requires approaches for tackling the energy supply variability. One approach is to use batteries and/or the electrical grid as a backup for the renewable energy. It may also be possible to adapt the workload to match the renewable energy supply. For highest benefits, green datacenter operators must intelligently manage their workloads and the sources of energy at their disposal.

In this paper, we first discuss the tradeoffs involved in building green datacenters today and in the future. Second, we present Parasol, a prototype green datacenter that we have built as a research platform. Parasol comprises a small container, a set of solar panels, a battery bank, and a grid-tie. Third, we describe GreenSwitch, our model-based approach for dynamically scheduling the workload and selecting the source of energy to use. Our real experiments with Parasol, GreenSwitch, and MapReduce workloads demonstrate that intelligent workload and energy source management can produce significant cost reductions. Our results also isolate the cost implications of peak power management, storing energy on the grid, and the ability to delay the MapReduce jobs. Finally, our results demonstrate that careful workload and energy source management can minimize the negative impact of electrical grid outages.
Power containers
Authors: Shen Kai , Shriraman Arrvindh , Dwarkadas Sandhya , Zhang Xiao , Chen Zhuan
Published: April 2020

Energy efficiency and power capping are critical concerns in server and cloud computing systems. They face growing challenges due to dynamic power variations from new client-directed web applications, as well as complex behaviors due to multicore resource sharing and hardware heterogeneity. This paper presents a new operating system facility called "power containers" that accounts for and controls the power and energy usage of individual fine-grained requests in multicore servers. This facility relies on three key techniques---1) online model that attributes multicore power (including shared maintenance power) to concurrently running tasks, 2) alignment of actual power measurements and model estimates to enable online model recalibration, and 3) on-the-fly application-transparent request tracking in multi-stage servers to isolate the power and energy contributions and customize per-request control. Our mechanisms enable new multicore server management capabilities including fair power capping that only penalizes power-hungry requests, and energy-aware request distribution between heterogeneous servers. Our evaluation uses three multicore processors (Intel Woodcrest, Westmere, and SandyBridge) and a variety of server and cloud computing (Google App Engine) workloads. Our results demonstrate the high accuracy of our request power accounting (no more than 11% errors) and the effectiveness of container-enabled power virus isolation and throttling. Our request distribution case study shows up to 25% energy saving compared to an alternative approach that recognizes machine heterogeneity but not fine-grained workload affinity.
Why you should care about quantile regression
Authors: de Oliveira Augusto Born , Fischmeister Sebastian , Diwan Amer , Hauswirth Matthias , Sweeney Peter F.
Published: April 2020

Research has shown that correctly conducting and analysing computer performance experiments is difficult. This paper investigates what is necessary to conduct successful computer performance evaluation by attempting to repeat a prior experiment: the comparison between two Linux schedulers.

In our efforts, we found that exploring an experimental space through a series of incremental experiments can be inconclusive, and there may be no indication of how much experimentation will be enough. Analysis of variance (ANOVA), a traditional analysis method, is able to partly solve the problems with the previous approach, but we demonstrate that ANOVA can be insufficient for proper analysis due to the requirements it imposes on the data.

Finally, we demonstrate the successful application of quantile regression, a recent development in statistics, to computer performance experiments. Quantile regression can provide more insight into the experiment than ANOVA, with the additional benefit of being applicable to data from any distribution. This property makes it especially useful in our field, since non-normally distributed data is common in computer experiments.
Discerning the dominant out-of-order performance advantage
Authors: McFarlin Daniel S. , Tucker Charles , Zilles Craig
Published: April 2020

In this paper, we set out to study the performance advantages of an Out-of-Order (OOO) processor relative to in-order processors with similar execution resources. In particular, we try to tease apart the performance contributions from two sources: the improved sched- ules enabled by OOO hardware speculation support and its ability to generate different schedules on different occurrences of the same instructions based on operand and functional unit availability. We find that the ability to express good static schedules achieves the bulk of the speedup resulting from OOO. Specifically, of the 53% speedup achieved by OOO relative to a similarly provisioned in- order machine, we find that 88% of that speedup can be achieved by using a single "best" static schedule as suggested by observing an OOO schedule of the code. We discuss the ISA mechanisms that would be required to express these static schedules. Furthermore, we find that the benefits of dynamism largely come from two kinds of events that influence the application's critical path: load instructions that miss in the cache only part of the time and branch mispredictions. We find that much of the benefit of OOO dynamism can be achieved by the potentially simpler task of addressing these two behaviors directly.
Verifying systems rules using rule-directed symbolic execution
Authors: Cui Heming , Hu Gang , Wu Jingyue , Yang Junfeng
Published: April 2020

Systems code must obey many rules, such as "opened files must be closed." One approach to verifying rules is static analysis, but this technique cannot infer precise runtime effects of code, often emitting many false positives. An alternative is symbolic execution, a technique that verifies program paths over all inputs up to a bounded size. However, when applied to verify rules, existing symbolic execution systems often blindly explore many redundant program paths while missing relevant ones that may contain bugs.

Our key insight is that only a small portion of paths are relevant to rules, and the rest (majority) of paths are irrelevant and do not need to be verified. Based on this insight, we create WOODPECKER, a new symbolic execution system for effectively checking rules on systems programs. It provides a set of builtin checkers for common rules, and an interface for users to easily check new rules. It directs symbolic execution toward the program paths relevant to a checked rule, and soundly prunes redundant paths, exponentially speeding up symbolic execution. It is designed to be heuristic-agnostic, enabling users to leverage existing powerful search heuristics.

Evaluation on 136 systems programs totaling 545K lines of code, including some of the most widely used programs, shows that, with a time limit of typically just one hour for each verification run, WOODPECKER effectively verifies 28.7% of the program and rule combinations over bounded input, whereas an existing symbolic execution system KLEE verifies only 8.5%. For the remaining combinations, WOODPECKER verifies 4.6 times as many relevant paths as KLEE. With a longer time limit, WOODPECKER verifies much more paths than KLEE,
e.g.,
17 times as many with a fourhour limit. WOODPECKER detects 113 rule violations, including 10 serious data loss errors with 2 most serious ones already confirmed by the corresponding developers.
Demand-based coordinated scheduling for SMP VMs
Authors: Kim Hwanju , Kim Sangwook , Jeong Jinkyu , Lee Joonwon , Maeng Seungryoul
Published: April 2020

As processor architectures have been enhancing their computing capacity by increasing core counts, independent workloads can be consolidated on a single node for the sake of high resource efficiency in data centers. With the prevalence of virtualization technology, each individual workload can be hosted on a virtual machine for strong isolation between co-located workloads. Along with this trend, hosted applications have increasingly been multithreaded to take advantage of improved hardware parallelism. Although the performance of many multithreaded applications highly depends on communication (or synchronization) latency, existing schemes of virtual machine scheduling do not explicitly coordinate virtual CPUs based on their communication behaviors.

This paper presents a demand-based coordinated scheduling scheme for consolidated virtual machines that host multithreaded workloads. To this end, we propose communication-driven scheduling that controls time-sharing in response to inter-processor interrupts (IPIs) between virtual CPUs. On the basis of in-depth analysis on the relationship between IPI communications and coordination demands, we devise IPI-driven coscheduling and delayed preemption schemes, which effectively reduce synchronization latency and unnecessary CPU consumption. In addition, we introduce a load-conscious CPU allocation policy in order to address load imbalance in heterogeneously consolidated environments. The proposed schemes are evaluated with respect to various scenarios of mixed workloads using the PARSEC multithreaded applications. In the evaluation, our scheme improves the overall performance of consolidated workloads, especially communication-intensive applications, by reducing inefficient synchronization latency.
Improving GPGPU concurrency with elastic kernels
Authors: Pai Sreepathi , Thazhuthaveetil Matthew J. , Govindarajan R.
Published: April 2020

Each new generation of GPUs vastly increases the resources available to GPGPU programs. GPU programming models (like CUDA) were designed to scale to use these resources. However, we find that CUDA programs actually do not scale to utilize all available resources, with over 30% of resources going unused on average for programs of the Parboil2 suite that we used in our work. Current GPUs therefore allow concurrent execution of kernels to improve utilization. In this work, we study concurrent execution of GPU kernels using multiprogram workloads on current NVIDIA Fermi GPUs. On two-program workloads from the Parboil2 benchmark suite we find concurrent execution is often no better than serialized execution. We identify that the lack of control over resource allocation to kernels is a major serialization bottleneck. We propose transformations that convert CUDA kernels into
elastic kernels
which permit fine-grained control over their resource usage. We then propose several elastic-kernel aware concurrency policies that offer significantly better performance and concurrency compared to the current CUDA policy. We evaluate our proposals on real hardware using multiprogrammed workloads constructed from benchmarks in the Parboil 2 suite. On average, our proposals increase system throughput (STP) by 1.21x and improve the average normalized turnaround time (ANTT) by 3.73x for two-program workloads when compared to the current CUDA concurrency implementation.
Protocol Responsibility Offloading to Improve TCP Throughput in Virtualized Environments
Authors: Gamage Sahan , Kompella Ramana Rao , Xu Dongyan , Kangarlou Ardalan
Published: April 2020

Virtualization is a key technology that powers cloud computing platforms such as Amazon EC2. Virtual machine (VM) consolidation, where multiple VMs share a physical host, has seen rapid adoption in practice, with increasingly large numbers of VMs per machine and per CPU core. Our investigations, however, suggest that the increasing degree of VM consolidation has serious negative effects on the VMs’ TCP performance. As multiple VMs share a given CPU, the scheduling latencies, which can be in the order of tens of milliseconds, substantially increase the typically submillisecond round-trip times (RTTs) for TCP connections in a datacenter, causing significant degradation in throughput. In this article, we propose a lightweight solution, called vPRO, that (a) offloads the VM’s TCP congestion control function to the driver domain to improve TCP transmit performance; and (b) offloads TCP acknowledgment functionality to the driver domain to improve the TCP receive performance. Our evaluation of a vPRO prototype on Xen suggests that vPRO substantially improves TCP receive and transmit throughputs with minimal per-packet CPU overhead. We further show that the higher TCP throughput leads to improvement in application-level performance, via experiments with Apache Olio, a Web 2.0 cloud application, and Intel MPI benchmark.
Inferring undesirable behavior from P2P traffic analysis
Authors: Torres Ruben D. , Hajjat Mohammad Y. , Rao Sanjay G. , Mellia Marco , Munafo Maurizio M.
Published: April 2020

While peer-to-peer (P2P) systems have emerged in popularity in recent years, their large-scale and complexity make them difficult to reason about. In this paper, we argue that systematic analysis of traffic characteristics of P2P systems can reveal a wealth of information about their behavior, and highlight potential undesirable activities that such systems may exhibit. As a first step to this end, we present an offline and semi-automated approach to detect undesirable behavior. Our analysis is applied on real traffic traces collected from a Point-of-Presence (PoP) of a national-wide ISP in which over 70% of the total traffic is due to eMule [19], a popular P2P file-sharing system. Flow-level measurements are aggregated into "samples" referring to the activity of each host during a time interval. We then employ a clustering technique to automatically and coarsely identify similar behavior across samples, and extensively use domain knowledge to interpret and analyze the resulting clusters. Our analysis shows several examples of undesirable behavior including evidence of DDoS attacks exploiting live P2P clients, significant amounts of unwanted traffic that may harm network performance, and instances where the performance of participating peers may be subverted due to maliciously deployed servers. Identification of such patterns can benefit network operators, P2P system developers, and actual end-users.
Redundancy in network traffic
Authors: Anand Ashok , Muthukrishnan Chitra , Akella Aditya , Ramjee Ramachandran
Published: April 2020

A large amount of popular content is transferred repeatedly across network links in the Internet. In recent years,
protocol-independent redundancy elimination
, which can remove duplicate strings from within arbitrary network flows, has emerged as a powerful technique to improve the efficiency of network links in the face of repeated data. Many vendors offer such redundancy elimination middleboxes to improve the effective bandwidth of enterprise, data center and ISP links alike.

In this paper, we conduct a large scale trace-driven study of protocol independent redundancy elimination mechanisms, driven by several terabytes of packet payload traces collected at 12 distinct network locations, including the access link of a large US-based university and of 11 enterprise networks of different sizes. Based on extensive analysis, we present a number of findings on the benefits and fundamental design issues in redundancy elimination systems. Two of our key findings are (1) A new redundancy elimination algorithm based on Winnowing that outperforms the widely-used Rabin fingerprint-based algorithm by 5-10% on most traces and by as much as 35% in some traces. (2) A surprising finding that 75-90% of middlebox's bandwidth savings in our enterprise traces is due to redundant byte-strings from within each client's traffic, implying that pushing redundancy elimination capability to the end hosts, i.e.
an end-to-end redundancy elimination solution
, could obtain most of the middlebox's bandwidth savings.