bluuebunny/crossref_metadata_2025 huggingface dataset:
Calcium maelstrom: recalcitrant hypocalcaemia following rapid correction of thyrotoxicosis, exacerbated by pregnancy
Authors: Shin Terry , Guerrero Arthur F
Published: May 2015

A 29-year-old pregnant woman with Graves’ disease presented with severe persistent hypocalcaemia after thyroidectomy. Six months prior to presentation she was diagnosed with Graves’ disease and remained uncontrolled with methimazole. She was confirmed pregnant prior to radioactive iodine ablation (RAI), and underwent total thyroidectomy during her second trimester. After surgery, continuous intravenous calcium infusion was required until delivery of the fetus allowed discontinuation at postoperative day 18, despite oral calcium and calcitriol administration. A total of 38 g of oral and 7.5 g of intravenous elemental calcium was administered. We report an unusual case of recalcitrant hypocalcaemia thought to be due to a combination of postoperative hypoparathyroidism, combined with thyrotoxic osteodystrophy and pregnancy, after surgical correction of Graves’ disease. Increased vigilance and early calcium supplementation should be a priority in the management of these patients.
Intermediate uveitis: an unusual presentation of cytomegalovirus intraocular infection in an immunocompetent patient
Authors: Amin Rowayda M , Ostheimer Trucian , Butler Nicholas J
Published: May 2015

We report a case of cytomegalovirus (CMV) intraocular infection in an otherwise healthy 51-year-old patient, presenting atypically as isolated intermediate uveitis without retinitis or retinal vasculitis. The patient had a confirmed CMV infection as a cause of her intraocular inflammation via PCR DNA testing of an aqueous sample. Appropriate oral antiviral therapy was initiated, and resulted in complete resolution of inflammation and improvement in visual acuity. Prophylactic therapy was instituted thereafter.
High-flow priapism following perineal trauma in a child
Authors: Burns Jessica , Rajendran Simon , Calder Alistair , Roebuck Derek
Published: May 2015

Priapism is a rare condition in children and can be classified as high or low flow. We present a case of traumatic high-flow priapism that was successfully managed by selective embolisation of a branch of the internal pudendal artery. The pertinent clinical features are antecedent trauma and prolonged painless partial erection. The investigation of choice is Doppler ultrasound. Management can either be conservative, radiological or surgical. While conservative management can be safely attempted for 6 weeks, given the nature of the condition, early intervention is often required. Radiological embolisation is the first line and is successful in 97% of cases. Surgery carries a higher morbidity and is only reserved in cases where repeated embolisation has failed. This case highlights the importance of a thorough history and careful interpretation of imaging with protocolised follow-up of patients by a paediatric urologist for early and accurate diagnosis of erectile dysfunction and prompt intervention to prevent future complications.
Severe acute pancreatitis after EUS-FNA of a pancreatic cyst: a rare, but serious complication
Authors: Jonkman Els F , van Tuyl Bas A C , Sanders Floris B M , Haas Lenneke E M
Published: May 2015

As a consequence of improved quality of abdominal imaging techniques in the last decades, discovery of pancreatic cystic lesions has become more common. The clinical significance of these lesions is often unclear and poses a diagnostic dilemma. Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) is a subject of debate regarding its role in the diagnostic evaluation of pancreatic masses and cysts. Although risks associated with the procedure are low, consequences can be serious and even life-threatening. We report a case of a previously healthy 59-year-old woman who suffered severe acute pancreatitis after EUS-FNA of a pancreatic cyst, requiring admission to the intensive care unit (ICU). Development of infected pancreatic necrosis and, successively, bowel ischaemia, led to multiple organ failure. Despite maximal antibiotic and surgical treatment the patient succumbed to refractory septic shock. The fatal outcome of this case illustrates the importance of balanced decision-making in the diagnostic approach of pancreatic cystic lesions.
More than a headache: a case of cetuximab-induced aseptic meningitis
Authors: Prasanna Devika , Elrafei Tarek , Shum Elaine , Strakhan Marianna
Published: May 2015

While the wide belief is that monoclonal antibodies, due to their large size, would not be able to penetrate the blood–brain barrier, we present a rare case of aseptic meningitis induced by intravenous cetuximab administration. A 58-year-old man with tonsillar squamous cell cancer presented with headache and fever, which started approximately 1 h after his first dose of cetuximab (loading dose of 400 mg/m2equalling 800 mg). CT scan of the head was non-revealing and laboratory tests including complete blood count, serum comprehensive metabolic panel and coagulation profile were within normal limits. Aseptic meningitis in the setting of cetuximab therapy has been reported on 6 previous occasions. Consistent with these prior reports, it is interesting to note that this case also occurred after administration of the initial higher loading dose of Cetuximab. This is of interest as Cetuximab is more frequently being dosed at 500 mg/m2(higher dose) every 2 weeks in colorectal cancer.
Postoperative cystoid macular oedema in a patient on fingolimod
Authors: Fan Gaskin Jennifer Chen-Chia , Coote Michael
Published: May 2015

We describe the first case of fingolimod-associated bilateral cystoid macular oedema (CMO) following uncomplicated cataract surgery. A 57-year-old woman has been on fingolimod for the past 2 years for the treatment of relapsing–remitting multiple sclerosis. She underwent uneventful consecutive cataract surgery 2 weeks apart. Three weeks following the second cataract operation, she reported gradual-onset blurred vision bilaterally. Examination revealed mildly reduced visual acuity and bilateral CMO. Treatment with topical corticosteroids and non-steroidal anti-inflammatory eye drops, as well as cessation of fingolimod in collaboration with the neurologist, resulted in complete resolution of the CMO. Patients on fingolimod are likely to be at increased risk of developing postoperative CMO.
Access all areas? An area-level analysis of accessibility to general practice and community pharmacy services in England by urbanity and social deprivation
Authors: Todd Adam , Copeland Alison , Husband Andy , Kasim Adetayo , Bambra Clare
Published: May 2015

Objectives

(1) To determine the percentage of the population in England that has access to a general practitioner (GP) premises within a 20 min walk (the accessibility); (2) explore the relationship between the walking distance to a GP premises and urbanity and social deprivation and (3) compare accessibility of a GP premises to that of a community pharmacy—and how this may vary by urbanity and social deprivation.

Design

This area-level analysis spatial study used postcodes for all GP premises and community pharmacies in England. Each postcode was assigned to a population lookup table and Lower Super Output Area (LSOA). The LSOA was then matched to urbanity (urban, town and fringe, or village, hamlet and isolated dwellings) and deprivation decile (using the Index of Multiple Deprivation score 2010).

Primary outcome measure

Living within a 20 min walk of a GP premises.

Results

Overall, 84.8% of the population is estimated to live within a 20 min walk of a GP premises: 81.2% in the most affluent areas, 98.2% in the most deprived areas, 94.2% in urban and 19.4% in rural areas. This is consistently lower when compared with the population living within a 20 min walk of a community pharmacy.

Conclusions

Our study shows that the vast majority of the population live within a 20 min walk of a GP premises, with higher proportions in the most deprived areas—a positive primary care law. However, more people live within a 20 min walk of a community pharmacy compared with a GP premises, and this potentially has implications for the commissioning of future services from these healthcare providers in England.
Is a haptic simulation interface more effective than computer mouse-based interface for neonatal intubation skills training?
Authors: Agarwal Anup , Leviter Julie , Mannarino Candace , Levit Orly , Johnston Lindsay , Auerbach Marc
Published: May 2015

Objective

To compare the efficacy of a three-dimensional (3D) haptic interface to a two-dimensional (2D) mouse interface for a screen-based simulation (SBS) neonatal intubation (NI) training intervention. Primary hypothesis: a haptic interface is more effective than a mouse interface for SBS training intervention for NI. Secondary hypothesis: SBS training, regardless of interface, will result in improved NI performance on a neonatal airway simulator.

Methods

45 participants were randomised to either a haptics or a mouse interface to complete an identical SBS training intervention for NI over a five-month period. Participants completed pre- and post-training surveys to assess demographics, experience, knowledge and attitudes. The primary outcome of participants’ NI skills performance was assessed on a neonatal manikin simulator. Skills were measured pre- and post- training by number of attempts and time to successfully intubate, and airway visualization.

Results

The demographics, training and experience were similar between groups. There was no difference in the improvement in skills, knowledge, attitudes or satisfaction ratings pre- and post-training between the groups. There was a significant decrease in number of attempts to intubate a neonatal airway simulator (2.89 vs 1.96, p<0.05) and improvement in the percent of subjects intubating in <30 seconds (22% vs 27%, p=0.02) from pre- to post-training in the study population overall.

Conclusion

Using a haptic interface did not have an advantage over a mouse interface in improving NI skills, knowledge, attitudes, or satisfaction. Overall, a SBS training intervention for NI improved skills measured on a neonatal airway simulator.
Republished: Ruptured distal AICA pseudoaneurysm presenting years after vestibular schwannoma resection and radiation
Authors: Mascitelli Justin R , McNeill Ian T , Mocco J , Berenstein Alejandro , DeMattia Joseph , Fifi Johanna T
Published: May 2015

Distal anterior inferior cerebellar artery (AICA) pseudoaneurysms are very rare lesions. Although cases have been previously reported, only a few have been reported as a result of vestibular schwannoma (VS) radiation, none have been reported as a result of VS resection, and only one has been reported as treated with parent vessel occlusion (PVO) with n-butyl cyanoacrylate (nBCA). We report a case of a 65-year-old man with a history of right-sided VS surgery and radiation who presented years later with a ruptured pseudoaneurysm of the distal right AICA and was treated with endovascular PVO using nBCA. The aneurysm was completely obliterated and the patient had no worsening of symptoms or neurological exam. The case illustrates a very rare complication of VS surgery and radiation as well as an effective treatment for distal AICA aneurysms.
Field evaluation of the performance of alternative deicers for winter maintenance of transportation facilities
Authors: Hossain S.M. Kamal , Fu Liping , Lake Roberto
Published: May 2015

This paper presents the results of an extensive field study on the comparative performance of alternative materials for snow and ice control of transportation facilities. Approximately 300 tests were conducted in a real-world environment, covering four alternative materials, and 21 snow events. Each of the alternatives tested were compared to regular rock salt in terms of snow melting performance — bare-pavement regain time. The study confirmed the relative advantage of these alternatives over the regular salt, but also showed that their performance varied largely depending on some external conditions. Performance models were calibrated and then used for developing application rate adjustment factors that can be applied by maintenance operations for determining the optimal application rates for specific weather events and pavement conditions. The applicability of the results is limited to parking lots and sidewalks without the traffic effects, and as such cannot be easily applied to winter roadways maintenance.
An economic analysis of seed source options under a changing climate for black spruce and white pine in Ontario, Canada
Authors: McKenney Daniel W. , Pedlar John H. , Yang Jing , Weersink Alfons , Lawrence Glenn
Published: May 2015

We present a model that maps the net present value (NPV) associated with planting black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) and white pine (Pinus strobus L.) seed sources across a study area centred on Ontario, Canada. The model accounts for climate change through the use of universal response functions, which (in principle) predict the growth of any seed source under any climatic conditions. We demonstrated the use of the model for two locations in northern Ontario; both species exhibited significant variation in NPV across the study area and significant gains associated with climate-smart seed movements. For example, the NPV associated with potential white pine seed sources varied by more than $1500·ha−1for a planting site at North Bay, Ontario. We also compared the NPV maps with climate similarity maps to examine the degree to which simple climate matching can act as a proxy for the detailed genecology relationships contained in the universal response functions. Overall, the climate similarity maps were well-correlated with the NPV maps; however, there was poor agreement regarding white pine seed deployment from North Bay, for which the two approaches identified opposite seed transfer directions. We propose that this situation can arise when species show strong adaptation to a central climatic optimum.
Segmented ionization chambers for beam monitoring in hadrontherapy
Authors: Braccini Saverio , Cirio Roberto , Donetti Marco , Marchetto Flavio , Pittà Giuseppe , Lavagno Marco , La Rosa Vanessa
Published: May 2015

Segmented ionization chambers represent a good solution to monitor the position, the intensity and the shape of ion beams in hadrontherapy. Pixel and strip chambers have been developed for both passive scattering and active scanning dose delivery systems. In particular, strip chambers are optimal for pencil beam scanning, allowing for spatial and time resolutions below 0.1 mm and 1 ms, respectively. The MATRIX pixel and the Strip Accurate Monitor for Beam Applications (SAMBA) detectors are described in this paper together with the results of several beam tests and industrial developments based on these prototypes.
Relating small neutrino masses and mixing
Authors: Pramanick Soumita , Raychaudhuri Amitava
Published: May 2015

Experiments on neutrino oscillations have uncovered several small parameters, θ13 being a prominent one. Others are the solar mass splitting vis-à-vis the atmospheric one and the deviation of θ23 from maximal mixing. In this talk, (talk given at the International Conference on Massive Neutrinos, Singapore, 9–13 February 2015) we elaborate on a neutrino mass model based on the see-saw mechanism in which the mixing angles to start with are either vanishing (θ13 and θ12) or π/4 (θ23). The atmospheric mass splitting is taken as a part of this initial structure but the solar splitting is absent. A perturbative contribution, originating from a Type-I see-saw, results in nonzero values of θ13, θ12, [Formula: see text], and shifts θ23 slightly from π/4, interrelating them all. The model incorporates CP-violation, the phase δ being close to 3π/2 for (a) quasidegeneracy or (b) inverted mass ordering. It will be put to test as the neutrino parameters get better determined.
Hidden stage of intracranial hemorrhage in newborn rats studied with laser speckle contrast imaging and wavelets
Authors: Pavlov Alexey N. , Abdurashitov Arkady S. , Pavlova Olga N. , Tuchin Valery V. , Sindeeva Olga S. , Sindeev Sergey S. , Semyachkina-Glushkovskaya Oxana V.
Published: May 2015

Using the laser speckle contrast imaging and wavelet-based analyses, we investigate a latent (a "hidden") stage of the development of intracranial hemorrhages (ICHs) in newborn rats. We apply two measures based on the continuous wavelet-transform of blood flow velocity in the sagittal sinus, namely, the spectral energy in distinct frequency ranges and a multiscality degree characterizing complexity of experimental data. We show that the wavelet-based multifractal formalism reveals changes in the cerebrovascular blood flow at the development of ICH.
The effect of ore roasting on arsenic oxidation state and solid phase speciation in gold mine tailings
Authors: Walker S.R. , Jamieson H.E. , Lanzirotti A. , Hall G.E.M. , Peterson R.C.
Published: May 2015

Metallurgical pretreatment of As-bearing ores involves oxidation of sulphides (most often As-bearing pyrite, arsenopyrite or enargite) resulting in complex oxidized As-bearing products. We have evaluated roasting pretreatment of arsenic-bearing ores in a broad context and related this to the specific operations at the Giant mine, Yellowknife, NWT, Canada, which roasted arsenopyrite (FeAsS)-rich gold ore concentrates during 50 years of operations. A large portion of the As was collected and stored in underground vaults as As
2
O
3
dust; however, some of the As was also released with tailings which contain concentrations between 1000 to 5000 ppm. Powder X-ray diffraction (XRD) and sequential extractions have been completed on samples of mill products and various ages of tailings at the Giant mine. These data along with petrographic and synchrotron μXRD and μX-ray absorption near-edge spectroscopy (μXANES) indicate that the largely oxidized roaster products (calcine) and electrostatic precipitator (ESP) dust host most of the As in the tailings with a lesser component of sulphide arsenic. The fine-grained nature of these oxidized products has led to hydraulic sorting within the tailings impounds and dispersal to downstream creek and lake sediments.
Measurement of
238
U/
235
U ratio in black spruce seedlings to fingerprint the source of uranium taken up by black spruce trees as a biogeochemical sampling medium
Authors: Nyade Praise K. , Wilton Derek H.C. , Thompson Gary M. , Longerich Henry P.
Published: May 2015

This study explored the measurement of
238
U/
235
U ratios in black spruce seedlings as a tracer to investigate the origin of U taken up by this biogeochemical sampling media. Inductively coupled plasma quadrupole mass spectrometer (ICP-QMS) and neutron activation (NAA) analyses of the
238
U/
235
U ratios in the total digested (HF/HNO
3
-aqua regia) portions of substrates (soil and peat) treated with 200 ml aliquots of 100, 250, and 400 mg/l of aqueous solutions of depleted uranium (DU) exhibited a substantial deviation from the accepted natural value of 137.88. Similarly, the measured
238
U/
235
U ratios in stems of seedlings grown in the DU-dosed substrates ranged from 174 to 210 and are linearly correlated with the dose of DU applied. The elevated
238
U/
235
U ratio in the seedlings suggests that U taken up by the plants is derived predominantly from the labile DU components in water rather than the component adsorbed onto mineral phases in the substrate. Consequently, it was concluded that the U contents in vegetation used as a biogeochemical sampling medium are derived from the labile components in groundwater and/or surface water. The precision and accuracy of the measured ratios were compared with the
238
U/
235
U ratios of in-house granite and uraninite reference samples.
A review of RST
VOLC
, an original algorithm for automatic detection and near-real-time monitoring of volcanic hotspots from space
Authors: Pergola N. , Coviello I. , Filizzola C. , Lacava T. , Marchese F. , Paciello R. , Tramutoli V.
Published: May 2015

The observation of volcanic thermal activity from space dates back to the late 1960s. Several methods have been proposed to improve detection and monitoring capabilities of thermal volcanic features, and to characterize them to improve our understanding of volcanic processes, as well as to inform operational decisions. In this paper we review the RST
VOLC
algorithm, which has been designed and implemented for automated detection and near-real-time monitoring of volcanic hotspots. The algorithm is based on the general Robust Satellite Techniques (RST) approach, representing an original strategy for satellite data analysis in the space–time domain. It has proven to be a useful tool for investigating volcanoes worldwide, by means of different satellite sensors, onboard polar orbiting and geostationary platforms. The RST
VOLC
rationale, its requirements and main operational capabilities are described here, together with the advantages of the tool and the known limitations. Results achieved through the study of two past eruptive events are shown, together with some recent examples demonstrating the near-continuous monitoring capability offered by RST
VOLC
. A summary is also made of the type products that the method is able to generate and provide. Lastly, the future perspectives, in terms of its possible implementation on the new generation of satellite systems, are briefly discussed.
The Effect of Compiler Optimizations on High-Level Synthesis-Generated Hardware
Authors: Huang Qijing , Lian Ruolong , Canis Andrew , Choi Jongsok , Xi Ryan , Calagar Nazanin , Brown Stephen , Anderson Jason
Published: May 2015

We consider the impact of compiler optimizations on the quality of high-level synthesis (HLS)-generated field-programmable gate array (FPGA) hardware. Using an HLS tool implemented within the state-of-the-art LLVM compiler, we study the effect of compiler optimizations on the hardware metrics of circuit area, execution cycles,
FMax
, and wall-clock time. We evaluate 56 different compiler optimizations implemented within LLVM and show that some optimizations significantly affect hardware quality. Moreover, we show that hardware quality is also affected by some optimization parameter values, as well as the order in which optimizations are applied. We then present a new HLS-directed approach to compiler optimizations, wherein we execute
partial
HLS and profiling at intermittent points in the optimization process and use the results to judiciously undo the impact of optimization passes predicted to be damaging to the generated hardware quality. Results show that our approach produces circuits with 16% better speed performance, on average, versus using the standard -O3 optimization level.
Automating Elimination of Idle Functions by Runtime Reconfiguration
Authors: Niu Xinyu , Chau Thomas C. P. , Jin Qiwei , Luk Wayne , Liu Qiang , Pell Oliver
Published: May 2015

A design approach is proposed to automatically identify and exploit runtime reconfiguration opportunities with optimised resource utilisation by eliminating idle functions. We introduce Reconfiguration Data Flow Graph, a hierarchical graph structure enabling reconfigurable designs to be synthesised in three steps: function analysis, configuration organisation, and runtime solution generation. The synthesised reconfigurable designs are dynamically evaluated and selected under various runtime conditions. Three applications—barrier option pricing, particle filter, and reverse time migration—are used in evaluating the proposed approach. The runtime solutions approximate their theoretical performance by eliminating idle functions and are 1.31 to 2.19 times faster than optimised static designs. FPGA designs developed with the proposed approach are up to 43.8 times faster than optimised CPU reference designs and 1.55 times faster than optimised GPU designs.
The Fine Classification of Conjunctive Queries and Parameterized Logarithmic Space
Authors: Chen Hubie , Müller Moritz
Published: May 2015

We perform a fundamental investigation of the complexity of conjunctive query evaluation from the perspective of parameterized complexity. We classify sets of Boolean conjunctive queries according to the complexity of this problem. Previous work showed that a set of conjunctive queries is fixed-parameter tractable precisely when the set is equivalent to a set of queries having bounded treewidth. We present a fine classification of query sets up to parameterized logarithmic space reduction. We show that, in the bounded treewidth regime, there are three complexity degrees and that the properties that determine the degree of a query set are bounded pathwidth and bounded tree depth. We also engage in a study of the two higher degrees via logarithmic space machine characterizations and complete problems. Our work yields a significantly richer perspective on the complexity of conjunctive queries and, at the same time, suggests new avenues of research in parameterized complexity.
Reflection without remorse
Authors: Ploeg Atze van der , Kiselyov Oleg
Published: May 2015

A series of list appends or monadic binds for many monads performs algorithmically worse when left-associated. Continuation-passing style (CPS) is well-known to cure this severe dependence of performance on the association pattern. The advantage of CPS dwindles or disappears if we have to examine or modify the intermediate result of a series of appends or binds, before continuing the series. Such examination is frequently needed, for example, to control search in non-determinism monads.

We present an alternative approach that is just as general as CPS but more robust: it makes series of binds and other such operations efficient regardless of the association pattern-- and also provides efficient access to intermediate results. The key is to represent such a conceptual sequence as an efficient sequence data structure. Efficient sequence data structures from the literature are homogeneous and cannot be applied as they are in a type-safe way to series of monadic binds. We generalize them to
type aligned sequences
and show how to construct their (assuredly order-preserving) implementations. We demonstrate that our solution solves previously undocumented, severe performance problems in iteratees, LogicT transformers, free monads and extensible effects.
The HdpH DSLs for scalable reliable computation
Authors: Maier Patrick , Stewart Robert , Trinder Phil
Published: May 2015

The statelessness of functional computations facilitates both parallelism and fault recovery. Faults and non-uniform communication topologies are key challenges for emergent large scale parallel architectures. We report on
HdpH
and
HdpH-RS
, a pair of Haskell DSLs designed to address these challenges for irregular task-parallel computations on large distributed-memory architectures. Both DSLs share an API combining explicit task placement with sophisticated work stealing. HdpH focuses on scalability by making placement and stealing topology aware whereas HdpH-RS delivers reliability by means of fault tolerant work stealing.

We present operational semantics for both DSLs and investigate conditions for semantic equivalence of HdpH and HdpH-RS programs, that is, conditions under which topology awareness can be transparently traded for fault tolerance. We detail how the DSL implementations realise topology awareness and fault tolerance. We report an initial evaluation of scalability and fault tolerance on a 256-core cluster and on up to 32K cores of an HPC platform.
A simple semantics for Haskell overloading
Authors: Morris J. Garrett
Published: May 2015

As originally proposed, type classes provide overloading and ad-hoc definition, but can still be understood (and implemented) in terms of strictly parametric calculi. This is not true of subsequent extensions of type classes. Functional dependencies and equality constraints allow the satisfiability of predicates to refine typing; this means that the interpretations of equivalent qualified types may not be interconvertible. Overlapping instances and instance chains allow predicates to be satisfied without determining the implementations of their associated class methods, introducing truly non-parametric behavior. We propose a new approach to the semantics of type classes, interpreting polymorphic expressions by the behavior of each of their ground instances, but without requiring that those behaviors be parametrically determined. We argue that this approach both matches the intuitive meanings of qualified types and accurately models the behavior of programs.
A Scalable, Correct Time-Stamped Stack
Authors: Dodds Mike , Haas Andreas , Kirsch Christoph M.
Published: May 2015

Concurrent data-structures, such as stacks, queues, and deques, often implicitly enforce a total order over elements in their underlying memory layout. However, much of this order is unnecessary: linearizability only requires that elements are ordered if the insert methods ran in sequence. We propose a new approach which uses timestamping to avoid unnecessary ordering. Pairs of elements can be left unordered if their associated insert operations ran concurrently, and order imposed as necessary at the eventual removal.

We realise our approach in a new non-blocking data-structure, the TS (timestamped) stack. Using the same approach, we can define corresponding queue and deque data-structures. In experiments on x86, the TS stack outperforms and outscales all its competitors -- for example, it outperforms the elimination-backoff stack by factor of two. In our approach, more concurrency translates into less ordering, giving less-contended removal and thus higher performance and scalability. Despite this, the TS stack is linearizable with respect to stack semantics.

The weak internal ordering in the TS stack presents a challenge when establishing linearizability: standard techniques such as linearization points work well when there exists a total internal order. We present a new stack theorem, mechanised in Isabelle, which characterises the orderings sufficient to establish stack semantics. By applying our stack theorem, we show that the TS stack is indeed linearizable. Our theorem constitutes a new, generic proof technique for concurrent stacks, and it paves the way for future weakly ordered data-structure designs.
Equations, Contractions, and Unique Solutions
Authors: Sangiorgi Davide
Published: May 2015

One of the most studied behavioural equivalences is bisimilarity. Its success is much due to the associated bisimulation proof method, which can be further enhanced by means of "up-to bisimulation" techniques such as "up-to context".

A different proof method is discussed, based on unique solution of special forms of inequations called contractions, and inspired by Milner's theorem on unique solution of equations. The method is as powerful as the bisimulation proof method and its "up-to context" enhancements. The definition of contraction can be transferred onto other behavioural equivalences, possibly contextual and noncoinductive.

This enables a coinductive reasoning style on such equivalences, either by applying the method based on unique solution of contractions, or by injecting appropriate contraction preorders into the bisimulation game. The techniques are illustrated on CCS-like languages; an example dealing with higher-order languages is also shown.
Space-Efficient Manifest Contracts
Authors: Greenberg Michael
Published: May 2015

The standard algorithm for higher-order contract checking can lead to unbounded space consumption and can destroy tail recursion, altering a program's asymptotic space complexity. While space efficiency for gradual types---contracts mediating untyped and typed code---is well studied, sound space efficiency for manifest contracts---contracts that check stronger properties than simple types, e.g., "is a natural'' instead of "is an integer''---remains an open problem.

We show how to achieve sound space efficiency for manifest contracts with strong predicate contracts. The essential trick is breaking the contract checking down into
coercions:
structured, blame-annotated lists of checks. By carefully preventing duplicate coercions from appearing, we can restore space efficiency while keeping the same observable behavior.
Quantitative Interprocedural Analysis
Authors: Chatterjee Krishnendu , Pavlogiannis Andreas , Velner Yaron
Published: May 2015

We consider the quantitative analysis problem for interprocedural control-flow graphs (ICFGs). The input consists of an ICFG, a positive weight function that assigns every transition a positive integer-valued number, and a labelling of the transitions (events) as good, bad, and neutral events. The weight function assigns to each transition a numerical value that represents a measure of how good or bad an event is. The quantitative analysis problem asks whether there is a run of the ICFG where the ratio of the sum of the numerical weights of good events versus the sum of weights of bad events in the long-run is at least a given threshold (or equivalently, to compute the maximal ratio among all valid paths in the ICFG). The quantitative analysis problem for ICFGs can be solved in polynomial time, and we present an efficient and practical algorithm for the problem.

We show that several problems relevant for static program analysis, such as estimating the worst-case execution time of a program or the average energy consumption of a mobile application, can be modeled in our framework. We have implemented our algorithm as a tool in the Java Soot framework. We demonstrate the effectiveness of our approach with two case studies. First, we show that our framework provides a sound approach (no false positives) for the analysis of inefficiently-used containers. Second, we show that our approach can also be used for static profiling of programs which reasons about methods that are frequently invoked. Our experimental results show that our tool scales to relatively large benchmarks, and discovers relevant and useful information that can be used to optimize performance of the programs.
Integrating Linear and Dependent Types
Authors: Krishnaswami Neelakantan R. , Pradic Pierre , Benton Nick
Published: May 2015

In this paper, we show how to integrate linear types with type dependency, by extending the linear/non-linear calculus of Benton to support type dependency. Next, we give an application of this calculus by giving a proof-theoretic account of imperative programming, which requires extending the calculus with computationally irrelevant quantification, proof irrelevance, and a monad of computations. We show the soundness of our theory by giving a realizability model in the style of Nuprl, which permits us to validate not only the beta-laws for each type, but also the eta-laws. These extensions permit us to decompose Hoare triples into a collection of simpler type-theoretic connectives, yielding a rich equational theory for dependently-typed higher-order imperative programs. Furthermore, both the type theory and its model are relatively simple, even when all of the extensions are considered.
Deep Specifications and Certified Abstraction Layers
Authors: Gu Ronghui , Koenig Jérémie , Ramananandro Tahina , Shao Zhong , Wu Xiongnan (Newman) , Weng Shu-Chun , Zhang Haozhong , Guo Yu
Published: May 2015

Modern computer systems consist of a multitude of abstraction layers (e.g., OS kernels, hypervisors, device drivers, network protocols), each of which defines an interface that hides the implementation details of a particular set of functionality. Client programs built on top of each layer can be understood solely based on the interface, independent of the layer implementation. Despite their obvious importance, abstraction layers have mostly been treated as a system concept; they have almost never been formally specified or verified. This makes it difficult to establish strong correctness properties, and to scale program verification across multiple layers.

In this paper, we present a novel language-based account of abstraction layers and show that they correspond to a strong form of abstraction over a particularly rich class of specifications which we call deep specifications. Just as data abstraction in typed functional languages leads to the important representation independence property, abstraction over deep specification is characterized by an important implementation independence property: any two implementations of the same deep specification must have contextually equivalent behaviors. We present a new layer calculus showing how to formally specify, program, verify, and compose abstraction layers. We show how to instantiate the layer calculus in realistic programming languages such as C and assembly, and how to adapt the CompCert verified compiler to compile certified C layers such that they can be linked with assembly layers. Using these new languages and tools, we have successfully developed multiple certified OS kernels in the Coq proof assistant, the most realistic of which consists of 37 abstraction layers, took less than one person year to develop, and can boot a version of Linux as a guest.
Specification Inference Using Context-Free Language Reachability
Authors: Bastani Osbert , Anand Saswat , Aiken Alex
Published: May 2015

We present a framework for computing context-free language reachability properties when parts of the program are missing. Our framework infers candidate specifications for missing program pieces that are needed for verifying a property of interest, and presents these specifications to a human auditor for validation. We have implemented this framework for a taint analysis of Android apps that relies on specifications for Android library methods. In an extensive experimental study on 179 apps, our tool performs verification with only a small number of queries to a human auditor.
Iris
Authors: Jung Ralf , Swasey David , Sieczkowski Filip , Svendsen Kasper , Turon Aaron , Birkedal Lars , Dreyer Derek
Published: May 2015

We present Iris, a concurrent separation logic with a simple premise: monoids and invariants are all you need. Partial commutative monoids enable us to express---and invariants enable us to enforce---user-defined *protocols* on shared state, which are at the conceptual core of most recent program logics for concurrency. Furthermore, through a novel extension of the concept of a *view shift*, Iris supports the encoding of *logically atomic specifications*, i.e., Hoare-style specs that permit the client of an operation to treat the operation essentially as if it were atomic, even if it is not.
Higher Inductive Types as Homotopy-Initial Algebras
Authors: Sojakova Kristina
Published: May 2015

Homotopy Type Theory is a new field of mathematics based on the recently-discovered correspondence between Martin-Löf's constructive type theory and abstract homotopy theory. We have a powerful interplay between these disciplines - we can use geometric intuition to formulate new concepts in type theory and, conversely, use type-theoretic machinery to verify and often simplify existing mathematical proofs.

Higher inductive types form a crucial part of this new system since they allow us to represent mathematical objects, such as spheres, tori, pushouts, and quotients, in the type theory. We investigate a class of higher inductive types called W-suspensions which generalize Martin-Löf's well-founded trees. We show that a propositional variant of W-suspensions, whose computational behavior is determined up to a higher path, is characterized by the universal property of being a homotopy-initial algebra. As a corollary we get that W-suspensions in the strict form are homotopy-initial.
Self-Representation in Girard's System U
Authors: Brown Matt , Palsberg Jens
Published: May 2015

In 1991, Pfenning and Lee studied whether System F could support a typed self-interpreter. They concluded that typed self-representation for System F "seems to be impossible", but were able to represent System F in F
ω
. Further, they found that the representation of F
ω
requires kind polymorphism, which is outside F
ω
. In 2009, Rendel, Ostermann and Hofer conjectured that the representation of kind-polymorphic terms would require another, higher form of polymorphism. Is this a case of infinite regress? We show that it is not and present a typed self-representation for Girard's System U, the first for a λ-calculus with decidable type checking. System U extends System F
ω
with kind polymorphic terms and types. We show that kind polymorphic types (i.e. types that depend on kinds) are sufficient to "tie the knot" -- they enable representations of kind polymorphic terms without introducing another form of polymorphism. Our self-representation supports operations that iterate over a term, each of which can be applied to a representation of itself. We present three typed self-applicable operations: a self-interpreter that recovers a term from its representation, a predicate that tests the intensional structure of a term, and a typed continuation-passing-style (CPS) transformation -- the first typed self-applicable CPS transformation. Our techniques could have applications from verifiably type-preserving metaprograms, to growable typed languages, to more efficient self-interpreters.
Conjugate Hylomorphisms -- Or
Authors: Hinze Ralf , Wu Nicolas , Gibbons Jeremy
Published: May 2015

The past decades have witnessed an extensive study of structured recursion schemes. A general scheme is the hylomorphism, which captures the essence of divide-and-conquer: a problem is broken into sub-problems by a coalgebra; sub-problems are solved recursively; the sub-solutions are combined by an algebra to form a solution. In this paper we develop a simple toolbox for assembling recursive coalgebras, which by definition ensure that their hylo equations have unique solutions, whatever the algebra. Our main tool is the conjugate rule, a generic rule parametrized by an adjunction and a conjugate pair of natural transformations. We show that many basic adjunctions induce useful recursion schemes. In fact, almost every structured recursion scheme seems to arise as an instance of the conjugate rule. Further, we adapt our toolbox to the more expressive setting of parametrically recursive coalgebras, where the original input is also passed to the algebra. The formal development is complemented by a series of worked-out examples in Haskell.
Polymorphic Functions with Set-Theoretic Types
Authors: Castagna Giuseppe , Nguyen Kim , Xu Zhiwu , Abate Pietro
Published: May 2015

This article is the second part of a two articles series about the definition of higher order polymorphic functions in a type system with recursive types and set-theoretic type connectives (unions, intersections, and negations).

In the first part, presented in a companion paper, we defined and studied the syntax, semantics, and evaluation of the explicitly-typed version of a calculus, in which type instantiation is driven by explicit instantiation annotations. In this second part we present a local type inference system that allows the programmer to omit explicit instantiation annotations for function applications, and a type reconstruction system that allows the programmer to omit explicit type annotations for function definitions.

The work presented in the two articles provides the theoretical foundations and technical machinery needed to design and implement higher-order polymorphic functional languages with union and intersection types and/or for semi-structured data processing.
Leveraging Weighted Automata in Compositional Reasoning about Concurrent Probabilistic Systems
Authors: He Fei , Gao Xiaowei , Wang Bow-Yaw , Zhang Lijun
Published: May 2015

We propose the first sound and complete learning-based compositional verification technique for probabilistic safety properties on concurrent systems where each component is an Markov decision process. Different from previous works, weighted assumptions are introduced to attain completeness of our framework. Since weighted assumptions can be implicitly represented by multi-terminal binary decision diagrams (MTBDD's), we give an L*-based learning algorithm for MTBDD's to infer weighted assumptions. Experimental results suggest promising outlooks for our compositional technique.
Higher-Order Approximate Relational Refinement Types for Mechanism Design and Differential Privacy
Authors: Barthe Gilles , Gaboardi Marco , Gallego Arias Emilio Jesús , Hsu Justin , Roth Aaron , Strub Pierre-Yves
Published: May 2015

Mechanism design is the study of algorithm design where the inputs to the algorithm are controlled by strategic agents, who must be incentivized to faithfully report them. Unlike typical programmatic properties, it is not sufficient for algorithms to merely satisfy the property, incentive properties are only useful if the strategic agents also believe this fact.

Verification is an attractive way to convince agents that the incentive properties actually hold, but mechanism design poses several unique challenges: interesting properties can be sophisticated relational properties of probabilistic computations involving expected values, and mechanisms may rely on other probabilistic properties, like differential privacy, to achieve their goals.

We introduce a relational refinement type system, called HOARe2, for verifying mechanism design and differential privacy. We show that HOARe2 is sound w.r.t. a denotational semantics, and correctly models (epsilon,delta)-differential privacy; moreover, we show that it subsumes DFuzz, an existing linear dependent type system for differential privacy. Finally, we develop an SMT-based implementation of HOARe2 and use it to verify challenging examples of mechanism design, including auctions and aggregative games, and new proposed examples from differential privacy.
Tractable Refinement Checking for Concurrent Objects
Authors: Bouajjani Ahmed , Emmi Michael , Enea Constantin , Hamza Jad
Published: May 2015

Efficient implementations of concurrent objects such as semaphores, locks, and atomic collections are essential to modern computing. Yet programming such objects is error prone: in minimizing the synchronization overhead between concurrent object invocations, one risks the conformance to reference implementations --- or in formal terms, one risks violating
observational refinement.
Testing this refinement even within a single execution is intractable, limiting existing approaches to executions with very few object invocations.

We develop a polynomial-time (per execution) approximation to refinement checking. The approximation is parameterized by an accuracy
k∈N
representing the degree to which refinement violations are visible. In principle, more violations are detectable as
k
increases, and in the limit, all are detectable. Our insight for this approximation arises from foundational properties on the partial orders characterizing the happens-before relations between object invocations: they are
interval orders,
with a well defined measure of complexity, i.e., their
length.
Approximating the happens-before relation with a possibly-weaker interval order of bounded length can be efficiently implemented by maintaining a bounded number of integer counters. In practice, we find that refinement violations can be detected with very small values of
k
, and that our approach scales far beyond existing refinement-checking approaches.
Ur/Web
Authors: Chlipala Adam
Published: May 2015

The World Wide Web has evolved gradually from a document delivery platform to an architecture for distributed programming. This largely unplanned evolution is apparent in the set of interconnected languages and protocols that any Web application must manage. This paper presents Ur/Web, a domain-specific, statically typed functional programming language with a much simpler model for programming modern Web applications. Ur/Web's model is unified, where programs in a single programming language are compiled to other "Web standards" languages as needed; supports novel kinds of encapsulation of Web-specific state; and exposes simple concurrency, where programmers can reason about distributed, multithreaded applications via a mix of transactions and cooperative preemption. We give a tutorial introduction to the main features of Ur/Web and discuss the language implementation and the production Web applications that use it.