bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinicopathological characteristics and management of colitis with anti-PD1 immunotherapy alone or in combination with ipilimumab
Authors: Nahar Kazi J , Rawson Robert V , Ahmed Tasnia , Tattersall Stephen , Sandanayake Neomal , Kiely Christopher J , Lo Serigne , Carlino Matteo , Palendira Umaimainthan , Scolyer Richard A , Long Georgina V , Menzies Alexander M
Published: November 2020

Background

Colitis is one of the common immune-related adverse events that leads to morbidity and treatment discontinuation of immunotherapy. The clinical presentation, endoscopic and histopathological features and best management of this toxicity are not well defined.

Patients and methods

Patients with metastatic melanoma who received immunotherapy (programmed cell death protein 1 (PD1) antibodies, alone or in combination with a cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibody (PD1 +CTLA-4)) and who developed clinically significant colitis (requiring systemic corticosteroids) were identified retrospectively from two academic centers. Clinical data were collected for all patients; endoscopic and histopathological data were examined in a subset.

Results

From May 2013 to May 2019, 118/1507 (7.8%) patients developed significant colitis; 80/553 (14.5%) after PD1+CTLA-4, 35/1000 (3.5%) PD1 alone, and three patients after Ipilimumab (IPI) alone. Combination therapy-induced colitis was more frequent (14.5% vs 3.5% in PD1 alone, p=<0.0001), had an earlier onset (6.3 weeks vs 25.7 weeks, p=<0.001), was more severe (grade 3/4 69% vs 31%, p=<0.001), and are more likely to require higher doses of steroids (91% vs 74%, p=0.01) than PD1 colitis. Among all patients treated with steroids (N=114), 54 (47%) responded and required no further therapy (steroid sensitive), 47 patients (41%) responded to infliximab (infliximab sensitive), and 13 (11%) were infliximab refractory and needed further immunosuppressive drugs. Infliximab-refractory patients all had onset within 4 weeks of immunotherapy commencement and were more likely to have an underlying autoimmune disease, have higher grade colitis, and require longer immunosuppression, yet had similar response and survival than other patients with colitis. Of 43 (37%) patients re-resumed treatment with PD1 monotherapy after colitis resolution, 16 (37%) of whom developed recurrent colitis. Endoscopic and histopathologic data were available for 64 patients. Most had left-sided colitis, with an increase in chronic inflammatory cells and neutrophils within the lamina propria, an increase in neutrophils in the surface epithelium, without increased lymphocytes or increased eosinophils. Infliximab-refractory colitis had a trend towards more confluent pancolitis with edema, erythema, ulceration, and absent vascularity with neutrophilic infiltration and erosion.

Conclusion

Clinically significant colitis varies in presentation, response to immunosuppression, and endoscopic/histologic features depending on the immunotherapy type. Infliximab-refractory colitis occurs early, is often high grade, and has adverse endoscopic and histopathologic features
Clinical profile and prognostic factors of alcoholic cardiomyopathy in tribal and non-tribal population
Authors: Dungdung Ajit , Kumar Abhinav , Guria Rishi Tuhin , Preetam Mukul , Tara Ruth K , Kumar Bindey , Saba Mohammad Kamal
Published: November 2020

Objective

Alcoholic cardiomyopathy (ACM) is a leading cause of non-ischaemic dilated cardiomyopathy (DCM) in tribal and non-tribal population. However, no study has been done depicting the correlation between clinical profile and prognosis of ACM in tribal and non-tribal population. This study also defines the long-term outcome and prognostic markers of ACM.

Methods

We studied 290 patients with ACM who were evaluated in our institute between January 2013 and December 2016. The primary endpoint of the study was all-cause mortality. Statistical analysis was done by using Kaplan-Meier survival curves for the assessment of all-cause mortality and Cox regression for the assessment of risk factors.

Results

After a median follow-up period of 3.75 years (IQR: 3–4 years), 50 patients with ACM (37.3%) died among tribal population while 14 patients (9%) died among non-tribal population. Independent predictors of all-cause mortality in ACM identified by Cox regression were left ventricular ejection fraction (LVEF) (HR: 0.883; 95% CI 0.783 to 0.996; p=0.043), QRS duration (HR: 1.010; 95% CI 1.007 to 1.017; p=0.005) and Child-Turcotte-Pugh (CTP) Scoring (HR: 12.332; 95% CI 6.999 to 21.728; p<0.001) at admission. The Kaplan-Meier survival probability estimate was 95.1% at 1 year and all-cause mortality was found to be higher in patients with QRS>120 ms, LVEF ≤35%, CTP Grade B/C than patients with QRS≤120 ms, LVEF >35% and CTP Score A, respectively (log-rank χ²=55.088, p<0.001; log-rank χ²=32.953, p<0.001; log-rank χ²=139.764, p<0.001, respectively).

Conclusion

Our study indicated increased morbidity and mortality in tribal population. LVEF, QRS duration and CTP Scoring at the time of presentation were found to be the independent prognostic markers of patients with ACM.
Symptoms, risk factors, diagnosis and treatment of urinary tract infections
Authors: Kaur Rajanbir , Kaur Rajinder
Published: November 2020

Urinary tract infection (UTI) is a common microbial infection found in all ages and sexes which involves inflammation of the urinary tract. These infections can range from simple bladder inflammation, that is, cystitis, to severe cases of uroseptic shock. UTI ranks as the number 1 infection that leads to a prescription of antibiotics after a doctor’s visit. These infections are sometimes distressing and even life threatening, and both males (12%) and females (40%) have at least one symptomatic UTI throughout their lives. Diagnostic failures in case of bacterial infections are the main contributing factor in improper use of antibiotics, delay in treatment and low survival rate in septic conditions. So, early diagnosis and appropriate therapy with antibiotics are the most significant requirements for preventing complicated UTI conditions such as urosepsis. This review article summarises the symptoms of the UTIs and the associated risk factors to it. The various conventional and recent diagnostic methods were also discussed in this review, along with treatment therapies with or without antibiotics.
iQOS: evidence of pyrolysis and release of a toxicant from plastic
Authors: Davis Barbara , Williams Monique , Talbot Prue
Published: November 2020

Objective

To evaluate performance of the I quit original smoking (iQOS) heat-not-burn system as a function of cleaning and puffing topography, investigate the validity of manufacturer’s claims that this device does not burn tobacco and determine if the polymer-film filter is potentially harmful.

Methods

iQOS performance was evaluated using five running conditions incorporating two different cleaning protocols. Heatsticks were visually and stereomicroscopically inspected preuse and postuse to determine the extent of tobacco plug charring (from pyrolysis) and polymer-film filter melting, and to elucidate the effects of cleaning on charring. Gas chromatography–mass spectrometry headspace analysis was conducted on unused polymer-film filters to determine if potentially toxic chemicals are emitted from the filter during heating.

Results

For all testing protocols, pressure drop decreased as puff number increased. Changes in testing protocols did not affect aerosol density. Charring due to pyrolysis (a form of organic matter thermochemical decomposition) was observed in the tobacco plug after use. When the manufacturer’s cleaning instructions were followed, both charring of the tobacco plug and melting of the polymer-film filter increased. Headspace analysis of the polymer-film filter revealed the release of formaldehyde cyanohydrin at 90°C, which is well below the maximum temperature reached during normal usage.

Discussion

Device usage limitations may contribute to decreases in interpuff intervals, potentially increasing user’s intake of nicotine and other harmful chemicals. This study found that the tobacco plug does char and that charring increases when the device is not cleaned between heatsticks. Release of formaldehyde cyanohydrin is a concern as it is highly toxic at very low concentrations.
Normally loaded inclined strip anchors in cohesionless soil
Authors: Al Hakeem Nabil , Aubeny Charles
Published: November 2020

Plate anchors are among the most effective anchorage systems that are widely used to resist horizontal and inclined uplift loads in many offshore and onshore applications. Previous research on plate anchors has largely focused on the horizontal or vertical breakout problems, with limited attention directed towards obtaining a full characterization of the effects of anchor orientation angle. The present study utilizes displacement-based finite element analyses to investigate the stability and performance of strip anchor embedded in cohesionless soil for plate inclination angles ranging from 0° to 90° from horizontal, where the applied load is normal to and acts at the center of the plate. This study investigates the effects of scale and roughness, along with the geometry of the failure mechanism for various plate orientations and embedment depths. The analyses, presented in terms of a non-dimensional breakout factor Nq, show that the breakout factor increases significantly with an increase in the inclination, especially for angles greater than 45° in loose sand and greater than 60° in dense sand. The analyses also show that scale effects (anchor width) can affect capacity. Finite element analyses have been used to introduce simple design charts relating the breakout factor to the embedment depth and relative density. Comparisons to experimental and numerical studies showed good agreement.
The thermochemical, structural, and spectroscopic analyses of the tautomers of sulfur and selenium modified emissive nucleobases
Authors: Parshotam Shyam , Joy Megan , Rossano-Tapia Maria , Mora-Gomez V. A. , Brown Alex
Published: November 2020

In this study, density functional theory (DFT) and time dependent density functional theory (TD-DFT) are used to investigate the stabilities and spectral properties [IR, UV–vis, and two-photon absorption (2PA)] of two sets of modified RNA nucleobase tautomers. The modifications introduce either a sulfur or selenium atom to form an isothiazolo[4,3-d]pyrimidine or isoselenazolo[4,3-d]pyrimidine heterocyclic core, respectively. The relative stabilities of both sets of modified tautomers determined with B3LYP/6-31++G(d,p) reveal that in water (with a polarizable continuum model), the 6-keto-2-amino tautomer of guanine and the rare 4-imino-2-keto tautomer of cytosine may be present at significant populations, whereas the 6-enol-2-amino tautomer of guanine is more common in the gas phase. The identification of these modified tautomers is possible due to the natural differences in their vibrational modes and hence IR spectra. Furthermore, the photophysical properties of both these sets of modified tautomers indicate that excitation and emission energies are shifted relative to their more abundant form in both one photon absorption and emission and 2PA spectra, as determined at the B3LYP/6-31++G(d,p) and CAM-B3LYP/aug-cc-pVDZ levels of theory, respectively. Even though the 2PA cross sections in water for all of the species are small (0.3–2.3 GM), the modified cytosine tautomer shows promise, as its cross section is larger than the more dominant form. The spectral separation between the dominant form and the tautomers of isoselenazole and isothiazole modified cytosine and guanine are relatively similar, suggesting both modifications could be useful in elucidating the tautomers from their more abundant counterparts.
Electromagnetic transition form factors, E2/M1 and C2/M1 ratios of the baryon decuplet
Authors: Kim June-Young , Kim Hyun-Chul
Published: November 2020

We investigate the electromagnetic transition form factors of the baryon decuplet to the baryon octet, based on the self-consistent SU(3) chiral quark-soliton model, taking into account the effects of explicit breaking of flavor SU(3) symmetry. We emphasize the $$Q^2$$

Q
2

dependence of the electromagnetic $$N\rightarrow \Delta $$

N
→
Δ

transition form factors and the ratios of E2/M1 and C2/M1 in comparison with the experimental and empirical data. In order to compare the present results of the electromagnetic transition form factors of the $$N\rightarrow \Delta $$

N
→
Δ

with those from lattice QCD, we evaluate the form factors with the pion mass deviated from its physical value. The results of the E2/M1 and C2/M1 ratios are in good agreement with the lattice data. We also present the results of the electromagnetic transition form factors for the decuplet to the octet transitions.
Improving Botulinum Toxin Efficiency in Treating Post-Stroke Spasticity Using 3D Innervation Zone Imaging
Authors: Zhang Chuan , Chen Yen-Ting , Liu Yang , Magat Elaine , Gutierrez-Verduzco Monica , Francisco Gerard E. , Zhou Ping , Li Sheng , Zhang Yingchun
Published: November 2020

Spasticity is a common post-stroke syndrome that imposes significant adverse impacts on patients and caregivers. This study aims to improve the efficiency of botulinum toxin (BoNT) in managing spasticity, by utilizing a three-dimensional innervation zone imaging (3DIZI) technique based on high-density surface electromyography (HD-sEMG) recordings. Stroke subjects were randomly assigned to two groups: the control group ([Formula: see text]) which received standard ultrasound-guided injections, and the experimental group ([Formula: see text]) which received 3DIZI-guided injections. The amount of BoNT given was consistent for all subjects. The Modified Ashworth Scale (MAS), compound muscle action potential (CMAP) and muscle activation volume (MAV) from bilateral biceps brachii muscles were obtained at the baseline, 3 weeks, and 3 months after injection. Intra-group and inter-group comparisons of MAS, CMAP amplitude and MAV were performed. An overall improvement in MAS of spastic elbow flexors was observed during the 3-week visit ([Formula: see text]), yet no statistically significant difference found with intra-group or inter-group analysis. Compared to the baseline, a significant reduction of CMAP amplitude and MAV were observed in the spastic biceps muscles of both groups at 3-week post-injection, and returned to approximate baseline value at 12-week post injection. A significantly higher reduction was found in CMAP amplitude ([Formula: see text]% versus [Formula: see text]%, [Formula: see text]) and MAV ([Formula: see text]% versus [Formula: see text]%, [Formula: see text]) in the experimental group compared to the control group. The study has demonstrated preliminary evidence that precisely directing BoNT to the innervation zones (IZs) localized by 3DIZI leads to a significantly higher treatment efficiency improvement in spasticity management. Results have also shown the feasibility of developing a personalized BoNT injection technique for the optimization of clinical treatment for post-stroke spasticity using proposed 3DIZI technique.
Geometric torsion, four-form, Riemann duals and Quintessence
Authors: Nitish R. , Kar Supriya
Published: November 2020

We revisit an emergent gravity scenario in [Formula: see text][Formula: see text][Formula: see text] dimensions underlying a propagating geometric torsion [Formula: see text] with a renewed interest. We show that a pair-symmetric [Formula: see text]th-order curvature tensor is sourced by Neveu–Schwarz (NS) two-form in a [Formula: see text] gauge theoretic formulation. Interestingly, the new spacetime curvature governs a torsion-free geometry sourced by an NS form and shares the properties of the Riemann tensor. On the other hand, a completely anti-symmetric [Formula: see text]th-order tensor in the formulation is shown to incorporate a dynamical geometric torsion and is argued to be identified with a nonperturbative correction. The four-form turns out to be [Formula: see text] gauge invariant underlying an onshell NS form. We show that an emergent gravity theory may elegantly be described with an axionic scalar presumably signifying a quintessence coupling to the Riemann-type geometries. The curvatures are appropriately worked out to obtain a [Formula: see text] emergent form theory. Investigation reveals that a pair of [Formula: see text]-brane is created across an event horizon. We show that an emergent [Formula: see text] theory in a decoupling limit identifies with the bosonic sector of [Formula: see text], Supergravity in [Formula: see text].
Space-distribution PDEs for path independent additive functionals of McKean–Vlasov SDEs
Authors: Ren Panpan , Wang Feng-Yu
Published: November 2020

Let [Formula: see text] be the space of probability measures on [Formula: see text] with finite second moment. The path independence of additive functionals of McKean–Vlasov SDEs is characterized by PDEs on the product space [Formula: see text] equipped with the usual derivative in space variable and Lions’ derivative in distribution. These PDEs are solved by using probabilistic arguments developed from Ref. 2. As a consequence, the path independence of Girsanov transformations is identified with nonlinear PDEs on [Formula: see text] whose solutions are given by probabilistic arguments as well. In particular, the corresponding results on the Girsanov transformation killing the drift term derived earlier for the classical SDEs are recovered as special situations.
Minima of independent time-inhomogeneous random walks
Authors: Hou Wanting , Hong Wenming
Published: November 2020

In this paper, we will consider the minima of an exponentially growing number of independent time-inhomogeneous random walks, where the first- and second-order limit behaviors for the minima have been obtained.
Effect of Internal Knowledge Sourcing on MNEs Subsidiaries’ Service Innovation Performance. The Role of Exploitative Learning and Entrepreneurial Orientation
Authors: Otoo Charles Oduro Acheampong , Li Wenyuan , Pomegbe Wisdom Wise Kwabla , Bamfo Bylon Abeeku , Dogbe Courage Simon Kofi
Published: November 2020

This study assessed the influence of internal knowledge sourcing on MNEs subsidiaries’ service innovation performance. It also considered the moderating role of entrepreneurial orientation, as well as the mediating role of exploitative learning. Empirical analysis was based on primary data gathered from 156 MNE subsidiaries. Various validity and reliability checks were conducted before the presentation of the actual analysis, which was conducted using Ordinary Least Squares approach, run using SPSS (v. 20). Findings indicate that, exploitative learning partially mediates the relationship between internal knowledge sourcing and MNE subsidiaries’ service innovation performance. Entrepreneurial orientation however, dampens the positive relationship between internal knowledge sourcing and exploitative learning. This study adds to the existing debate in the arena of knowledge-based view of the firm.
The Five Stages of Evolution of Inter-Organisational Networks: A Review of the Literature
Authors: Kempner-Moreira Fernanda , Freire Patricia de Sá
Published: November 2020

Inter-organisational networks are presented as an adequate response to the dynamic and innovative environment in which organisations are inserted. It is necessary to develop dynamic capabilities to operate in single, double or triple cycle learning networks. However, there is no awareness of how networks can evolve in this fluid and agile environment of contemporary society. The purpose of this paper is to identify the stages of evolution of the Inter-organisational Networks and their constituent elements. Five stages of network evolution were identified: exchange, development, expansion, action and learning. This integrative literature review points out the characteristics of each of these stages, also listing its constituent elements. The Inter-organisational Learning Network is presented as the stage where learning becomes one of the objectives of the network and not just one of its results, which enhances its gains. The document contributes to a reflection on the stages of networks and strategies necessary for its evolution, where the results are more lasting. Acting in networks is necessary and being aware of the actions necessary for this strategy to generate better results contributes to more effective solutions.
Fabrication of In2O3-SnS2 Core–Shell Heterojunction for Efficient Photocatalytic Removal of Hexavalent Chromium
Authors: Lei Ze-Xiao , Yang Feng-Yi , Yuan Cong , Tai Lang , Yao Chang-Yu , Fang Dong
Published: November 2020

The development of heterojunction composites with core–shell structure could effectively facilitate the separation of carriers. In this work, a novel In2O3-SnS2 (IOS) core–shell heterojunction photocatalyst was successfully synthesized for the efficient photocatalytic reduction of hexavalent chromium (Cr(VI)), namely, the In2O3 nanorods were obtained through successive hydrothermal and carbonization process using urea and glucose as template. Then, SnS2 nanosheets were successfully in situ coated onto In2O3 nanorods. The spectroscopic characterization and photo-electrochemistry test indicated that the IOS core–shell heterojunction could effectively accelerate the separation and transport of carriers and suppress the recombination of carriers. The photocatalytic performance of IOS was evaluated by photocatalytic reduction Cr(VI). The results showed that IOS-4 samples almost completely removed Cr(VI) (20 mg/L), within 90 min under visible light, which was superior to pure In2O3 and SnS2. Furthermore, IOS samples also possess excellent stability, the removal efficiency was still maintained at 90% after five cycles. This work provided a reliable method for designing core–shell heterojunctions for the photocatalytic removal of Cr(VI) under visible light.
Enhanced electrical conductivity in Zr-Doped (La0.7Ba0.3)(Mn0.5Fe0.5)O3 solid solutions
Authors: Kumar Yogesh , Pal Jaswinder , Malhi Parambir Singh , Kumar Rakesh
Published: November 2020

The perovskite ([Formula: see text][Formula: see text]([Formula: see text][Formula: see text][Formula: see text]O3, where [Formula: see text] = 0.1, 0.2 and 0.3, ceramics were synthesized by solid-state reaction method. The introductory structural studies were followed through by X-ray diffraction technique and the results have disclosed that all the samples were crystallized into an isolated phase. The Zr substitution in the resulting solid solutions increases the electrical conductivity and the maximum value of ac conductivity has been found to be [Formula: see text]118.8 S [Formula: see text] cm[Formula: see text] for [Formula: see text] = 0.3 at 200[Formula: see text]C (at 1 MHz). The frequency dependence of ac conductivity data follows Jonscher’s power law. The variation of the exponent [Formula: see text] versus temperature follows the nonoverlapping small polaron tunneling (NSPT) model. The dielectric relaxation has been observed to be of non-Debye nature for all measuring temperatures (50–200[Formula: see text]C). The impedance spectroscopy reveals that all the samples exhibit negative temperature coefficient of resistance (NTCR) behavior. The prepared samples (for [Formula: see text] > 1) are supposed to be suitable for cathode materials in SOFCs.
Bismuth zinc niobate: BZN-BT, a new lead-free BaTiO3-based ferroelectric relaxor?
Authors: Marshall Jessica , Walker David , Thomas Pam
Published: November 2020

The novel lead-free ferroelectric relaxor system [Formula: see text](Bi([Formula: see text] [Formula: see text][Formula: see text](1[Formula: see text]BaTiO3([Formula: see text]BZN(1[Formula: see text]BT) has received interest as a high-capacity relaxor dielectric material. Small quantities (< 10.0 mol.%) of BZN-based dopant had significant impacts on the structure of the BaTiO3host. This study evaluates the effect of BZN additions to the BaTiO3host up to [Formula: see text]BZN = 10.0%. Initial additions of BZN were observed to stabilize tetragonal and orthorhombic coexistence at 295 K, alongside increasing dielectric constant. Peak dielectric constant and polarization were observed at [Formula: see text] < 4.0%, coinciding with maximum orthorhombic intensity and a local minima in tetragonal intensity. Compositions 0 < [Formula: see text] < 4.0% showed increasing polarization and a drop in [Formula: see text] and classical ferroelectric properties. No significant dielectric dispersion was observed for compositions [Formula: see text] < 4.0% over the frequency range 5–640 kHz. Compositions at [Formula: see text] > 4.0% showed the onset of dielectric relaxation alongside a drop in polarization coincident with a drop in the tetragonal [Formula: see text]/[Formula: see text] ratio and the onset of the cubic phase at 295 K. Peak piezoelectric, dielectric and polarization values occurred over the range 3.8% < [Formula: see text] < 4.0%, alongside maximum orthorhombic intensity. Subsequent BZN additions showed a rapid onset of dielectric relaxation, alongside an increase in cubic intensity and a continuous drop in [Formula: see text] with a minima near [Formula: see text] = 7.0%. Tetragonal presence at 295 K also vanished to zero at [Formula: see text] = 7.0%. Polarization loops ceased showing ferroelectric characteristics at [Formula: see text] > 5.0%, showing a transition from lossy relaxor dielectric to low-loss relaxor dielectric at [Formula: see text] > 10.0%.
Survey on Localization Systems and Algorithms for Unmanned Systems
Authors: Yuan Shenghai , Wang Han , Xie Lihua
Published: November 2020

Intelligent unmanned systems have important applications, such as pesticide-spraying in agriculture, robot-based warehouse management systems, and missile-firing drones. The underlying assumption behind all autonomy is that the agent knows its relative position or egomotion with respect to some reference or scene. There exist thousands of localization systems in the literature. These localization systems use various combinations of sensors and algorithms, such as visual/visual-inertial SLAM, to achieve robust localization. The majority of the methods use one or more sensors from LIDAR, camera, IMU, UWB, GPS, compass, tracking system, etc. This survey presents a systematic review and analysis of published algorithms and techniques chronologically, and we introduce various highly impactful works. We provide insightful investigation and taxonomy on sensory data forming principle, feature association principle, egomotion estimation formation, and fusion model for each type of system. At last, some open problems and directions for future research are also included. We aim to survey the literature comprehensively to provide a complete understanding of localization methodologies, performance, advantages and limitations, and evaluations of various methods, shedding some light for future research.
Topological Circuits - A Stepping Stone in the Topological Revolution
Authors: Xun Russell Yang Qi
Published: November 2020

The 2016 Nobel prize in physics was awarded to the pioneers who studied topological systems in Condensed Matter Physics such as the Quantum Hall Effect, where edge currents in a material are restricted to discrete values. Topology was developed to study geometric structures where only global properties are of concern (like the number of holes in an object). It has since been applied to physical systems with remarkable success; such as circuit theory. In this project, Kirchhoff’s Laws are reformulated so that circuits can be analysed using the powerful tool of topology. This sheds light on the properties of exotic real materials such as graphene[24]. The quantum edge effect in a polyacetylene chain happens only when the edge of the chain is conducting. This was recreated experimentally using electrical circuits. Physical laws govern the properties of the bulk in a material to that of the edge. However, dissipation introduced into circuits using voltage controlled current sources was shown to have broken these laws. Results are attributed to boundary conditions affecting all states in the bulk, not just edge states, implying a new state of matter. Studying Condensed matter systems using electrical circuits gives physicists an accessible, scalable and inexpensive way to study real materials.
Analysis of a Queueing Model for Energy Storage Systems with Self-discharge
Authors: Raeis Majid , Burchard Almut , Liebeherr Jörg
Published: November 2020

This article presents an analysis of a recently proposed queueing system model for energy storage with discharge. Even without a load, energy storage systems experience a reduction of the stored energy through
self-discharge
. In some storage technologies, the rate of self-discharge can exceed 50% of the stored energy per day. We consider a queueing model, referred to as
leakage queue
, where, in addition to an arrival and a service process, there is a leakage process that reduces the buffer content by a factor ɣ ( 0 < ɣ < 1) in each time slot. When the average drift is positive, we discover that the leakage queue operates in one of two regimes, each with distinct characteristics. In one of the regimes, the stored energy always stabilizes at a point that lies below the storage capacity, and the stored energy closely follows a Gaussian distribution. In the other regime, the storage system behaves similar to a conventional finite capacity system. For both regimes, we derive expressions for the probabilities of underflow and overflow. In particular, we develop a new martingale argument to estimate the probability of underflow in the second regime. The methods are validated in a numerical example where the energy supply resembles a wind energy source.
BiNeTClus
Authors: Bouguessa Mohamed , Nouri Khaled
Published: November 2020

We investigate the problem of community detection in bipartite networks that are characterized by the presence of two types of nodes such that connections exist only between nodes of different types. While some approaches have been proposed to identify community structures in bipartite networks, there are a number of problems still to solve. In fact, the majority of the proposed approaches suffer from one or even more of the following limitations: (1) difficulty in detecting communities in the presence of many non-discriminating nodes with atypical connections that hide the community structures, (2) loss of relevant topological information due to the transformation of the bipartite network to standard plain graphs, and (3) manually specifying several input parameters, including the number of communities to be identified. To alleviate these problems, we propose BiNeTClus, a parameter-free community detection algorithm in bipartite networks that operates in two phases. The first phase focuses on identifying an initial grouping of nodes through a transactional data model capable of dealing with the situation that involves networks with many atypical connections, that is, sparsely connected nodes and nodes of one type that massively connect to all other nodes of the second type. The second phase aims to refine the clustering results of the first phase via an optimization strategy of the bipartite modularity to identify the final community structures. Our experiments on both synthetic and real networks illustrate the suitability of the proposed approach.
Certified and efficient instruction scheduling: application to interlocked VLIW processors
Authors: Six Cyril , Boulmé Sylvain , Monniaux David
Published: November 2020

CompCert is a moderately optimizing C compiler with a formal, machine-checked, proof of correctness: after successful compilation, the assembly code has a behavior faithful to the source code. Previously, it only supported target instruction sets with sequential semantics, and did not attempt reordering instructions for optimization.

We present here a CompCert backend for a VLIW core (
i.e.
with explicit parallelism at the instruction level), the first CompCert backend providing scalable and efficient instruction scheduling. Furthermore, its highly modular implementation can be easily adapted to other VLIW or non-VLIW pipelined processors.
How do programmers use unsafe rust?
Authors: Astrauskas Vytautas , Matheja Christoph , Poli Federico , Müller Peter , Summers Alexander J.
Published: November 2020

Rust’s ownership type system enforces a strict discipline on how memory locations are accessed and shared. This discipline allows the compiler to statically prevent memory errors, data races, inadvertent side effects through aliasing, and other errors that frequently occur in conventional imperative programs. However, the restrictions imposed by Rust’s type system make it difficult or impossible to implement certain designs, such as data structures that require aliasing (e.g. doubly-linked lists and shared caches). To work around this limitation, Rust allows code blocks to be declared as
unsafe
and thereby exempted from certain restrictions of the type system, for instance, to manipulate C-style raw pointers. Ensuring the safety of unsafe code is the responsibility of the programmer. However, an important assumption of the Rust language, which we dub the
Rust hypothesis
, is that programmers use Rust by following three main principles: use unsafe code sparingly, make it easy to review, and hide it behind a safe abstraction such that client code can be written in safe Rust.

Understanding how Rust programmers use unsafe code and, in particular, whether the Rust hypothesis holds is essential for Rust developers and testers, language and library designers, as well as tool developers. This paper studies empirically how unsafe code is used in practice by analysing a large corpus of Rust projects to assess the validity of the Rust hypothesis and to classify the purpose of unsafe code. We identify queries that can be answered by automatically inspecting the program’s source code, its intermediate representation MIR, as well as type information provided by the Rust compiler; we complement the results by manual code inspection. Our study supports the Rust hypothesis partially: While most unsafe code is simple and well-encapsulated, unsafe features are used extensively, especially for interoperability with other languages.
Handling bidirectional control flow
Authors: Zhang Yizhou , Salvaneschi Guido , Myers Andrew C.
Published: November 2020

Pressed by the difficulty of writing asynchronous, event-driven code, mainstream languages have recently been building in support for a variety of advanced control-flow features. Meanwhile, experimental language designs have suggested effect handlers as a unifying solution to programmer-defined control effects, subsuming exceptions, generators, and async–await. However, despite these trends, complex control flow—in particular, control flow that exhibits a bidirectional pattern—remains challenging to manage.

We introduce bidirectional algebraic effects, a new programming abstraction that supports bidirectional control transfer in a more natural way. Handlers of bidirectional effects can raise further effects to transfer control back to the site where the initiating effect was raised, and can use themselves to handle their own effects. We present applications of this expressive power, which falls out naturally as we push toward the unification of effectful programming with object-oriented programming. We pin down the mechanism and the unification formally using a core language that makes generalizations to effect operations and effect handlers.

The usual propagation semantics of control effects such as exceptions conflicts with modular reasoning in the presence of effect polymorphism—it breaks parametricity. Bidirectionality exacerbates the problem. Hence, we set out to show the core language, which builds on the existing tunneling semantics for algebraic effects, is not only type-safe (no effects go unhandled), but also abstraction-safe (no effects are accidentally handled). We devise a step-indexed logical-relations model, and construct its parametricity and soundness proofs. These core results are fully mechanized in Coq. While a full-featured compiler is left to future work, experiments show that as a first-class language feature, bidirectional handlers can be implemented efficiently.
Formulog: Datalog for SMT-based static analysis
Authors: Bembenek Aaron , Greenberg Michael , Chong Stephen
Published: November 2020

Satisfiability modulo theories (SMT) solving has become a critical part of many static analyses, including symbolic execution, refinement type checking, and model checking. We propose Formulog, a domain-specific language that makes it possible to write a range of SMT-based static analyses in a way that is both close to their formal specifications and amenable to high-level optimizations and efficient evaluation.

Formulog extends the logic programming language Datalog with a first-order functional language and mechanisms for representing and reasoning about SMT formulas; a novel type system supports the construction of expressive formulas, while ensuring that neither normal evaluation nor SMT solving goes wrong. Our case studies demonstrate that a range of SMT-based analyses can naturally and concisely be encoded in Formulog, and that — thanks to this encoding — high-level Datalog-style optimizations can be automatically and advantageously applied to these analyses.
A model for detecting faults in build specifications
Authors: Sotiropoulos Thodoris , Chaliasos Stefanos , Mitropoulos Dimitris , Spinellis Diomidis
Published: November 2020

Incremental and parallel builds are crucial features of modern build systems. Parallelism enables fast builds by running independent tasks simultaneously, while incrementality saves time and computing resources by processing the build operations that were affected by a particular code change. Writing build definitions that lead to error-free incremental and parallel builds is a challenging task. This is mainly because developers are often unable to predict the effects of build operations on the file system and how different build operations interact with each other. Faulty build scripts may seriously degrade the reliability of automated builds, as they cause build failures, and non-deterministic and incorrect outputs.

To reason about arbitrary build executions, we present BuildFS, a generally-applicable model that takes into account the specification (as declared in build scripts) and the actual behavior (low-level file system operation) of build operations. We then formally define different types of faults related to incremental and parallel builds in terms of the conditions under which a file system operation violates the specification of a build operation. Our testing approach, which relies on the proposed model, analyzes the execution of single full build, translates it into BuildFS, and uncovers faults by checking for corresponding violations.

We evaluate the effectiveness, efficiency, and applicability of our approach by examining 612 Make and Gradle projects. Notably, thanks to our treatment of build executions, our method is the first to handle JVM-oriented build systems. The results indicate that our approach is (1) able to uncover several important issues (247 issues found in 47 open-source projects have been confirmed and fixed by the upstream developers), and (2) much faster than a state-of-the-art tool for Make builds (the median and average speedup is 39X and 74X respectively).
Guided linking: dynamic linking without the costs
Authors: Bartell Sean , Dietz Will , Adve Vikram S.
Published: November 2020

Dynamic linking is extremely common in modern software systems, thanks to the flexibility and space savings it offers. However, this flexibility comes at a cost: it’s impossible to perform interprocedural optimizations that involve calls to a dynamic library. The basic problem is that the run-time behavior of the dynamic linker can’t be predicted at compile time, so the compiler can make no assumptions about how such calls will behave.

This paper introduces
guided linking
, a technique for optimizing dynamically linked software when some information about the dynamic linker’s behavior is known in advance. The developer provides an arbitrary set of programs, libraries, and plugins to our tool, along with
constraints
that limit the possible dynamic linking behavior of the software. By taking advantage of the constraints, our tool enables
any
existing optimization to be applied across dynamic linking boundaries. For example, the NoOverride constraint can be applied to a function when the developer knows it will never be overridden with a different definition at run time; guided linking then enables the function to be inlined into its callers in other libraries. We also introduce a novel code size optimization that deduplicates identical functions even across different parts of the software set.

By applying guided linking to the Python interpreter and its dynamically loaded modules, supplying the constraint that no other programs or modules will be used, we increase speed by an average of 9%. By applying guided linking to a dynamically linked distribution of Clang and LLVM, and using the constraint that no other software will use the LLVM libraries, we can increase speed by 5% and reduce file size by 13%. If we relax the constraint to allow other software to use the LLVM libraries, we can still increase speed by 5% and reduce file size by 5%. If we use guided linking to combine 11 different versions of the Boost library, using minimal constraints, we can reduce the total library size by 57%.
Igloo: soundly linking compositional refinement and separation logic for distributed system verification
Authors: Sprenger Christoph , Klenze Tobias , Eilers Marco , Wolf Felix A. , Müller Peter , Clochard Martin , Basin David
Published: November 2020

Lighthouse projects like CompCert, seL4, IronFleet, and DeepSpec have demonstrated that full system verification is feasible by establishing a refinement between an abstract system specification and an executable implementation. Existing approaches however impose severe restrictions on the abstract system specifications due to their limited expressiveness or versatility, or on the executable code due to their use of suboptimal code extraction or inexpressive program logics. We propose a novel methodology that combines the compositional refinement of event-based models of distributed systems with the verification of full-fledged program code using expressive separation logics, which support features of realistic programming languages like heap data structures and concurrency. Our main technical contribution is a formal framework that soundly relates event-based system models to program specifications in separation logics. This enables protocol development tools to soundly interoperate with program verifiers to establish a refinement between the model and the code. We formalized our framework, Igloo, in Isabelle/HOL. We report on three case studies, a leader election protocol, a replication protocol, and a security protocol, for which we refine formal requirements into program specifications that we implement in Java and Python and prove correct using the VeriFast and Nagini tools.
Verifying and improving Halide’s term rewriting system with program synthesis
Authors: Newcomb Julie L. , Adams Andrew , Johnson Steven , Bodik Rastislav , Kamil Shoaib
Published: November 2020

Halide is a domain-specific language for high-performance image processing and tensor computations, widely adopted in industry. Internally, the Halide compiler relies on a term rewriting system to prove properties of code required for efficient and correct compilation. This rewrite system is a collection of handwritten transformation rules that incrementally rewrite expressions into simpler forms; the system requires high performance in both time and memory usage to keep compile times low, while operating over the undecidable theory of integers. In this work, we apply formal techniques to prove the correctness of existing rewrite rules and provide a guarantee of termination. Then, we build an automatic program synthesis system in order to craft new, provably correct rules from failure cases where the compiler was unable to prove properties. We identify and fix 4 incorrect rules as well as 8 rules which could give rise to infinite rewriting loops. We demonstrate that the synthesizer can produce better rules than hand-authored ones in five bug fixes, and describe four cases in which it has served as an assistant to a human compiler engineer. We further show that it can proactively improve weaknesses in the compiler by synthesizing a large number of rules without human supervision and showing that the enhanced ruleset lowers peak memory usage of compiled code without appreciably increasing compilation times.
Dynamic dispatch of context-sensitive optimizations
Authors: Poesia Gabriel , Pereira Fernando Magno Quintão
Published: November 2020

Academia has spent much effort into making context-sensitive
analyses
practical, with great profit. However, the implementation of context-sensitive
optimizations
, in contrast to analyses, is still not practical, due to code-size explosion. This growth happens because current technology requires the cloning of full paths in the Calling Context Tree. In this paper, we present a solution to this problem. We combine finite state machines and dynamic dispatching to allow fully context-sensitive specialization while cloning only functions that are effectively optimized. This technique makes it possible to apply very liberal optimizations, such as context-sensitive constant propagation, in large programs—something that could not have been easily done before. We demonstrate the viability of our idea by formalizing it in Prolog, and implementing it in LLVM. As a proof of concept, we have used our state machines to implement context-sensitive constant propagation in LLVM. The binaries produced by traditional full cloning are 2.63 times larger than the binaries that we generate with our state machines. When applied on Mozilla Firefox, our optimization increases binary size from 7.2MB to 9.2MB. Full cloning, in contrast, yields a binary of 34MB.
Deductive optimization of relational data storage
Authors: Feser John , Madden Sam , Tang Nan , Solar-Lezama Armando
Published: November 2020

Optimizing the physical data storage and retrieval of data are two key database management problems. In this paper, we propose a language that can express both a relational query and the layout of its data. Our language can express a wide range of physical database layouts, going well beyond the row- and column-based methods that are widely used in database management systems. We use deductive program synthesis to turn a high-level relational representation of a database query into a highly optimized low-level implementation which operates on a specialized layout of the dataset. We build an optimizing compiler for this language and conduct experiments using a popular database benchmark, which shows that the performance of our specialized queries is better than a state-of-the-art in memory compiled database system while achieving an order-of-magnitude reduction in memory use.