bluuebunny/crossref_metadata_2025 huggingface dataset:
In-Situ Fracture Tolerance of the Metatarsals During Quasi-Static Compressive Loading of the Human Foot
Authors: Kalra Mayank , Bahensky Robert , McLachlin Stewart D. , Cronin Duane S. , Chandrashekar Naveen
Published: October 2021

Accidental foot injuries including metatarsal fractures commonly result from compressive loading. The ability of personal protective equipment to prevent these traumatic injuries depends on the understanding of metatarsal fracture tolerance. However, the in situ fracture tolerance of the metatarsals under direct compressive loading to the foot's dorsal surface remains unexplored, even though the metatarsals are the most commonly fractured bones in the foot. The goal of this study was to quantify the in situ fracture tolerance of the metatarsals under simulated quasi-static compressive loading. Fresh-frozen cadaveric feet (n = 10) were mounted into a testing apparatus to replicate a natural stance and loaded at the midmetatarsals with a cylindrical bar to simulate a crushing-type injury. A 900 N compressive force was initially applied, followed by 225 N successive load increments. Specimens were examined using X-ray imaging between load increments to assess for the presence of metatarsal fractures. Descriptive statistics were conducted for metatarsal fracture force and deformation. Pearson correlation tests were used to quantify the correlation between fracture force with age and body mass index (BMI). The force and deformation at fracture were 1861 ± 642 N (mean ± standard deviation) and 22.6 ± 3.4 mm, respectively. Fracture force was correlated with donor BMI (r = 0.90). Every fractured specimen experienced a transverse fracture in the second metatarsal. New biomechanical data from this study further quantify the metatarsal fracture risk under compressive loading and will help to improve the development and testing of improved personal protective equipment for the foot to avoid catastrophic injury.
Numerical Simulation and Modeling Convention of Unsteady Fluidelastic Forces of Tube Arrays
Authors: Zhang Mingjie , Wang Xu , Øiseth Ole
Published: October 2021

This paper presents a numerical investigation on the unsteady fluidelastic forces of tube arrays. The key focus is on the consistency between the unsteady fluidelastic force model and the quasi-steady model for tube arrays at large reduced flow velocities, as well as comparing two well-known conventions for the unsteady model. Two-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) simulations are used to prove that the viscous damping coefficients of Tanaka's convention approach their quasi-steady values as the reduced flow velocity approaches infinity, whereas the hysteretic damping coefficients of Chen's modified convention always approach zero and hence result in low-resolution data plots as the reduced flow velocity becomes large. The nonconstant viscous damping coefficients of Tanaka's experimental data at high reduced flow velocities (which motivated the introduction of Chen's modified convention) might be induced by a systematic identification error in the phase of the fluidelastic force. A row of three flexible cylinders is used as a numerical example to analyze the effect of systematic phase error on the predicted stability boundary of the fluidelastic instability. Although identical fluidelastic forces are simulated by using the two conventions, Tanaka's convention is recommended due to its compatibility with the quasi-steady theory and optimal resolutions of data plots over any range of reduced flow velocities.
A Practical Analysis Framework for Assessment of Printed Circuit Heat Exchangers in High-Temperature Nuclear Service
Authors: Shaw Avinash , Mahajan Heramb P. , Hassan Tasnim
Published: October 2021

Printed circuit heat exchangers (PCHEs) have high thermal efficiency because of the numerous minuscule channels. These minuscule channels result in a high thermal exchange area per unit volume, making PCHE a top contender for an intermediate heat exchanger (IHX) in high-temperature reactors. Thousands of minuscule channels make finite element analysis of the PCHE computationally infeasible. A two-dimensional analysis is usually performed for the PCHE core, which cannot simulate the local channel level responses reasonably because of the absence of global constraint influence. At present, there is no analysis technique available in the ASME Code or literature that is computationally efficient and suitable for engineers to estimate PCHE local responses. A novel but practical two-step analysis framework is proposed for performing PCHE analysis. In the first step, the channeled core is replaced by orthotropic solids with similar stiffness to simulate the global thermomechanical elastic responses of the PCHE. In the second step, local submodel analysis with detailed channel geometry and loading is performed using the elastic-perfectly plastic (EPP) material model. The proposed two-step analysis technique provides a unique capability to estimate the channel corner responses to be used for PCHE performance assessment. This study first developed a methodology for calculating the elastic orthotropic properties of the PCHE core. Next, the two-step analysis is performed for a realistic size PCHE core, and different issues observed in the results are scrutinized and resolved. Finally, a practical finite element analysis framework for PCHEs in high-temperature nuclear service is recommended.
Fibrillar Collagen: A Review of the Mechanical Modeling of Strain-Mediated Enzymatic Turnover
Authors: Topol Heiko , Demirkoparan Hasan , Pence Thomas J.
Published: October 2021

Collagen is the most abundant protein in mammals, often serving as the main load bearing constituent in soft tissues. Collagen undergoes continuous remodeling processes in which present collagen degrades, and new collagen is formed and deposited. Experiments find that modestly strained fibrillar collagen is often stabilized to enzymatic degradation, a mechanism that is essential in approaching and maintaining a homeostatic balance in the tissue remodeling process for healthy tissue. At larger strains, this decline in the collagen degradation rate may be reversed. This article reviews different modeling approaches that seek to account for the effect of straining on collagen remodeling, both with respect to collagen amount and to resulting mechanical properties. These models differ in the considered length scale starting from the molecular scale up to the larger continuum scale.
Exploring Female University Athlete Experiences of Coping With Protracted Concussion Symptoms
Authors: Steins Rebecca M. , Bloom Gordon , Caron Jeffrey
Published: October 2021

Concussions result in a multitude of somatic, cognitive, and/or emotional symptoms as well as physical and behavior changes and disturbances in balance, cognition, and sleep. Moreover, some concussed athletes can experience these symptoms, changes, and disturbances for extended periods of time. This qualitative study explored the coping skills used by five female university athletes who suffered persistent concussion symptoms for more than 6 weeks. Our analysis of the interview data indicated that the athletes used emotion-focused coping strategies, such as avoidance and acceptance, throughout their recovery. In addition, the lack of perceived control over their injuries, a lack of a symptom-specific treatment protocol, and the type of social support they received influenced their coping abilities. These results add to the limited, yet growing, body of literature on the psychology of sport-related concussions, particularly with respect to identifying the types of resources that athletes may use to cope and manage concussion symptoms.
Selective trade-offs maintain alleles underpinning complex trait variation in plants
Authors: Troth Ashley , Puzey Joshua R. , Kim Rebecca S. , Willis John H. , Kelly John K.
Published: October 2021

Fluctuating selection in nature

Natural environmental variation can lead to individuals within a species experiencing different selective parameters. Seep monkeyflower (
Mimulus guttatus
) populations are constrained by local moisture availability and the onset of summer drought. This results in a selective tradeoff between the amount of seed set, which is determined by plant size, and the timing of reproduction. Troth
et al.
sequenced and phenotyped 187
M. guttatus
plants and identified genetic variants associated with plant and flower size and rapid flowering. In wild populations surveyed over 3 years, the magnitude of selection changed depending on the rainfall patterns. Thus, fluctuating selection may maintain genetic variation in this species.

Science
, this issue p.
475
A call for seagrass protection
Authors: Cullen-Unsworth Leanne C. , Unsworth Richard
Published: October 2021

Seagrass conservation is crucial for climate mitigation, biodiversity protection, and food security.
Bioelectric signaling and the control of cardiac cell identity in response to mechanical forces
Authors: Fukui Hajime , Chow Renee Wei-Yan , Xie Jing , Foo Yoke Yin , Yap Choon Hwai , Minc Nicolas , Mochizuki Naoki , Vermot Julien
Published: October 2021

Making cardiac valves via mechanical forces

Cardiac valves form in response to mechanical forces generated by the beating heart. Fukui
et al
. studied how patterning signals are generated in response to these forces (see the Perspective by Jain and Epstein). They show that two mechanotransduction pathways act in parallel to instruct cardiac valve progenitors: a well-established transient receptor potential mechanosensation pathway and an extracellular ATP-dependent purinergic receptor pathway that triggers Ca
2+
oscillations and results in nuclear translocation of the protein nuclear factor of activated T cells 1. These two synergistic mechanotransduction pathways generate positional information and control valve formation. The use of multiple pathways may be a general mechanism used by mechanosensitive biological systems to increase the robustness and precision of mechanotransduction. —BAP
Heuristics in the delivery room
Authors: Singh Manasvini
Published: October 2021

Decisions about delivery

Heuristics, or simplified decision rules, have been found to influence decision-making in several settings. Singh found that when patients experience a complication during birth either via vaginal or cesarean delivery, their doctors are more likely to switch to the opposite delivery mode for their next patient’s birth (see the Perspective by Li and Colby). There is also evidence that this heuristic may lead to worse patient outcomes. —TSR
Comment on “Reintroduction of the archaic variant of
NOVA1
in cortical organoids alters neurodevelopment”
Authors: Maricic Tomislav , Helmbrecht Nelly , Riesenberg Stephan , Macak Dominik , Kanis Philipp , Lackner Martin , Pugach-Matveeva Agrafena Daria , Pääbo Svante
Published: October 2021

Trujillo
et al
. (Research Articles, 12 February 2021, eaax2537) conclude that the reintroduction of an ancestral amino acid substitution in the protein NOVA1 drastically alters the development of brain organoids. We show that cell lines used by the authors carry heterozygous deletions of the target DNA sequence, providing another plausible explanation for the effects observed.
Univariate classification of phosphine ligation state and reactivity in cross-coupling catalysis
Authors: Newman-Stonebraker Samuel H. , Smith Sleight R. , Borowski Julia E. , Peters Ellyn , Gensch Tobias , Johnson Heather C. , Sigman Matthew S. , Doyle Abigail G.
Published: October 2021

Which phosphines squeeze together?

Phosphine ligands coordinated to palladium and nickel are essential tools for assembling the backbones of pharmaceutical compounds. For decades, descriptors that characterize spatial bulk have helped to guide phosphine optimization. However, these descriptors tend to apply to ideal geometries of a single ligand. Newman-Stonebraker
et al
. introduce a descriptor that considers how the ligand conformation might change in a crowded environment. Specifically, they found that the minimum percentage buried volume accurately predicts when one or two of a particular ligand will coordinate to a metal center, frequently a key determinant of successful catalysis. —JSY
Toward an understanding of structural racism: Implications for criminal justice
Authors: Rucker Julian M. , Richeson Jennifer A.
Published: October 2021

Racial inequality is a foundational feature of the criminal justice system in the United States. Here we offer a psychological account for how Americans have come to tolerate a system that is so at odds with their professed egalitarian values. We argue that beliefs about the nature of racism—as being solely due to prejudiced individuals rather than structural factors that disadvantage marginalized racial groups—work to uphold racial stratification in the criminal justice system. Although acknowledging structural racism facilitates the perception of and willingness to reduce racial inequality in criminal justice outcomes, many Americans appear willfully ignorant of structural racism in society. We reflect on the role of psychological science in shaping popular understandings of racism and discuss how to contribute more meaningfully to its reduction.
No more trial and error for zeolites
Authors: Chaikittisilp Watcharop , Okubo Tatsuya
Published: October 2021

A data-intensive approach scours known organics for synthesizing targeted zeolites
The benefits of disturbance
Authors: Roman Joe
Published: October 2021

Physical disruption of an ecosystem by sea otters affects the genetic diversity of their habitat
New observatory to bring soil up from the deep
Authors: Stokstad Erik
Published: October 2021

Ecotron will move 3-meter cores into the laboratory for global change experiments
Activation of CaMKIV by soluble amyloid-β
1–42
impedes trafficking of axonal vesicles and impairs activity-dependent synaptogenesis
Authors: Park Daehun , Na Myeongsu , Kim Jung Ah , Lee Unghwi , Cho Eunji , Jang Mirye , Chang Sunghoe
Published: October 2021

Amyloid-β impairs synaptic function in neurons by inhibiting intersynaptic vesicular trafficking.
Paper of note in
Science
357
(6346)
Authors: VanHook Annalisa M.
Published: October 2021

This week’s article offers a possible explanation for how Zika virus causes microcephaly.
Novel Symbiotic Genome-Scale Model Reveals
Wolbachia
's Arboviral Pathogen Blocking Mechanism in Aedes aegypti
Authors: Jiménez Natalia E. , Gerdtzen Ziomara P. , Olivera-Nappa Álvaro , Salgado J. Cristian , Conca Carlos
Published: October 2021

Arboviral diseases such as Zika and Dengue have been on the rise mainly due to climate change, and the development of new treatments and strategies to limit their spreading is needed. The use of
Wolbachia
as an approach for disease control has motivated new research related to the characterization of the mechanisms that underlie its pathogen-blocking properties.
A Novel
Toxoplasma
Inner Membrane Complex Suture-Associated Protein Regulates Suture Protein Targeting and Colocalizes with Membrane Trafficking Machinery
Authors: Chern Jessica H. , Pasquarelli Rebecca R. , Moon Andy S. , Chen Allan L. , Sha Jihui , Wohlschlegel James A. , Bradley Peter J.
Published: October 2021

The inner membrane complex (IMC) is a peripheral membrane and cytoskeletal system that is organized into intriguing rectangular plates at the periphery of the parasite. The IMC plates are delimited by an array of IMC suture proteins that are tethered to both the membrane and the cytoskeleton and are thought to provide structure to the organelle.
Morphological and Transcriptional Responses to CRISPRi Knockdown of Essential Genes in Escherichia coli
Authors: Silvis Melanie R. , Rajendram Manohary , Shi Handuo , Osadnik Hendrik , Gray Andrew N. , Cesar Spencer , Peters Jason M. , Hearne Cameron C. , Kumar Parth , Todor Horia , Huang Kerwyn Casey , Gross Carol A.
Published: October 2021

Essential genes make up only ∼5 to 10% of the genetic complement in most organisms but occupy much of their protein synthesis and account for almost all antibiotic targets. Despite the importance of essential genes, their intractability has, until recently, hampered efforts to study them.
Undifferentiated pleomorphic sarcoma of the chest wall: a rare diagnosis
Authors: Sahu Swarnita , Halder Shikha , Jain Sunila , Koul Rakesh Kumar
Published: October 2021

A 31-year-old man with no predisposing factors and no history of chronic disease presented with a small painless lump over his anterior chest wall. On evaluation, it was found to be undifferentiated pleomorphic sarcoma. He underwent wide local excision of the tumour with clear margins, followed by adjuvant radiotherapy. At 6-month follow-up, the patient is clinically and radiologically disease free.
Hearing hoofbeats? Think head and neck trauma: a 10-year NTDB analysis of equestrian-related trauma in the USA
Authors: Mutore Kevin , Lim Jiyun , Fofana Demba , Torres-Reveron Annelyn , Skubic Jeffrey J
Published: October 2021

Objective

There is a paucity of evidence about traumatic injuries and their sequelae sustained due to equestrian injuries nationally.

Methods

Retrospective study analyzing National Trauma Data Bank data from 2007 to 2016. Variables collected included age, sex, race, payer status, Injury Severity Score (ISS), hospital length of stay, Glasgow Coma Scale, systolic blood pressure (SBP) at presentation, discharge disposition, and mortality. Patient data were analyzed by anatomic region.

Results

The most frequent type of injury was in the thorax, but head and neck injuries produced the highest mortality. Increased ISS and an SBP of less than 90 mm Hg were also significant predictors of mortality.

Conclusions

The risk of hospital admission from equestrian injuries is higher than football, motor vehicle racing, and skiing. Preventive measures and campaigns should be instituted to highlight safety practices and the use of personal protective equipment while on horseback either for sports, leisure, or work.

Level of evidence

Level IV. Retrospective study.
Synchrony in population dynamics of juvenile Atlantic salmon: analyzing spatiotemporal variation and the influence of river flow and demography
Authors: Bouchard Colin , Buoro Mathieu , Lebot Clément , Carlson Stephanie M.
Published: October 2021

Dispersal and shared environmental conditions can both synchronize the dynamics of local populations, but disentangling their relative influence on dynamics is challenging. We used a Bayesian approach to estimate the synchrony of a metapopulation of Atlantic salmon (Salmo salar) composed of 18 populations in Brittany, France, including a 24-year time series of the abundances of juveniles. We estimated the spatial synchrony at a regional and local spatial scale over the study period. We found a strong regional synchrony despite spatiotemporal variability of local synchrony in the abundance of juveniles. We then explored the drivers of synchrony, including environmental conditions (aspects of river flow) and abundance of adult breeders. This revealed that summer low-flow conditions seemed to synchronize the abundances of juveniles more than the synchrony in the abundance of adult breeders, suggesting a Moran effect. Given that drought conditions are expected to become more common with climate change, our work highlights the potentially strong synchronizing effect of summer low flow on the dynamics of local salmon populations and the benefits of considering synchrony at multiple scales.
One-Dimensional Convolutional Neural Networks Combined with Channel Selection Strategy for Seizure Prediction Using Long-Term Intracranial EEG
Authors: Wang Xiaoshuang , Zhang Guanghui , Wang Ying , Yang Lin , Liang Zhanhua , Cong Fengyu
Published: October 2021

Seizure prediction using intracranial electroencephalogram (iEEG) has attracted an increasing attention during recent years. iEEG signals are commonly recorded in the form of multiple channels. Many previous studies generally used the iEEG signals of all channels to predict seizures, ignoring the consideration of channel selection. In this study, a method of one-dimensional convolutional neural networks (1D-CNN) combined with channel selection strategy was proposed for seizure prediction. First, we used 30-s sliding windows to segment the raw iEEG signals. Then, the 30-s iEEG segments, which were in three channel forms (single channel, channels only from seizure onset or free zone and all channels from seizure onset and free zones), were used as the inputs of 1D-CNN for classification, and the patient-specific model was trained. Finally, the channel form with the best classification was selected for each patient. The proposed method was evaluated on the Freiburg Hospital iEEG dataset. In the situation of seizure occurrence period (SOP) of 30[Formula: see text]min and seizure prediction horizon (SPH) of 5[Formula: see text]min, 98.60[Formula: see text] accuracy, 98.85[Formula: see text] sensitivity and 0.01/h false prediction rate (FPR) were achieved. In the situation of SOP of 60[Formula: see text]min and SPH of 5[Formula: see text]min, 98.32[Formula: see text] accuracy, 98.48[Formula: see text] sensitivity and 0.01/h FPR were attained. Compared with the many existing methods using the same iEEG dataset, our method showed a better performance.
The impact of negative edges on spreading in signed networks
Authors: Zhang Peng , Zhang Xiao , Xue Leyang
Published: October 2021

In signed networks, negative edges represent negative relationships; the increase or gathering of negative interpersonal relationships can lead to social turmoil, which will affect the spreading of diseases or information. Therefore, it is significant to study the impact of the proportion and configuration of negative edges on spreading. In this paper, to study the impact of negative relationships on spreading, we propose a heterogeneous spreading model using signed networks. In this model, we use the balance of the local structure to quantify the probability of contact between individuals, making the contacts heterogeneous. We then examine the impact of negative edges on spreading using numerical simulations. We find that the balance of the network and the spreading coverage (i.e. outbreak size) gradually decrease with the proportion of negative edges. Compared with preference configurations (in which negative signs are placed on edges that have an important impact on spreading), a random configuration (in which negative signs are placed on random edges) has a suppressive effect on spreading. This provides information for epidemic prevention. Finally, we find that there are two important factors — contact probability and spreading paths — that could explain the observed spreading phenomena.
THE CONSTRUCTION AND APPLICATION OF FINANCIAL STRESS INDEX IN CHINA
Authors: SONG YUCHEN , LI FANGYAN
Published: October 2021

Maintaining the stability of the financial system is of great significance to a country’s economic security, and accurate measurement of systemic financial risks is the basic premise. This paper selects nine important factor index data in China’s five markets, uses the credit weight method and extreme value method to construct a time-sensitive China financial stress index. It is concluded that the change of the financial stress index precedes the change of the economic development trend, which proves the guiding significance of constructing the stress index to economic development. Finally, reasonable suggestions were put forward to relevant departments.
Geodesics and bending of light around a BTZ black hole surrounded by quintessential matter
Authors: Kala Shubham , Nandan Hemwati , Sharma Prateek , Elmardi Maye
Published: October 2021

Various observations from cosmic microwave background radiation (CMBR), type Ia supernova and baryon acoustic oscillations (BAO) are strongly suggestive of an accelerated expansion of the universe which can be explained by the presence of mysterious energy known as dark energy. The quintessential matter coupled with gravity minimally is considered one of the possible candidates to represent the presence of such dark energy in our universe. In view of this scenario, we study the geodesic of massless particles as well as massive particles around a (2 + 1)-dimensional BTZ black hole (BH) spacetime surrounded by the quintessence. The effect of parameters involved in the deflection of light by such a BH spacetime is investigated in detail. The results obtained are then compared with a usual non-rotating BTZ BH spacetime.
Micro-pattern gaseous detectors in high-energy and astroparticle physics
Authors: Sauli Fabio
Published: October 2021

Introduced in the late 70s of the last century, a new generation of position-sensitive sensors named micro-pattern gaseous detectors (MPGDs) allows to detect and localize ionizing radiation with sub-mm accuracy and high-rate capability. Performing and reliable, MPGDs are gradually replacing detection systems based on multiwire proportional chambers, and find applications in particle physics, astrophysics, plasma diagnostics and other fields.
Emergent gravity from stochastic fluctuations
Authors: Erlich Joshua
Published: October 2021

It is possible that both the classical description of spacetime and the rules of quantum field theory emerge from a more-fundamental structure of physical law. Pregeometric frameworks transfer some of the puzzles of quantum gravity to a semiclassical arena where those puzzles pose less of a challenge. However, in order to provide a satisfactory description of quantum gravity, a semiclassical description must emerge and contain in its description a macroscopic spacetime geometry, dynamical matter, and a gravitational interaction consistent with general relativity at long distances. In this essay, we argue that a framework that includes a stochastic origin for quantum field theory can provide both the emergence of classical spacetime and a quantized gravitational interaction.
MACHINABILITY ASSESSMENT OF SHAPE MEMORY ALLOY NITINOL DURING WEDM OPERATION: APPLICATION POTENTIAL OF TAGUCHI BASED AHP–DFA TECHNIQUE
Authors: MAJUMDER HIMADRI , KHAN AKHTAR , NAIK DEEPAK KUMAR , KUMAR CH. SATEESH
Published: October 2021

This paper exemplifies the feasibility of expanding a multi-criteria decision-making (MCDM) method to select optimum process parameters during the wire electrical discharge machining (WEDM) of nitinol. The application potential of combined desirability function analysis (DFA) and analytical hierarchy process (AHP) has been reported. Nitinol, a shape memory alloy (SMA), can memorize or retain its original shape when subjected to thermo-mechanical or magnetic loads. Four key input variables, like pulse on time ([Formula: see text], pulse off time ([Formula: see text], wire tension (WT), and wire feed (WF) have been studied to optimize three correlated responses, like kerf width, material removal rate (MRR), and surface roughness ([Formula: see text]. Process parameter permutations [Formula: see text]s, [Formula: see text]s, [Formula: see text] kg-F and [Formula: see text][Formula: see text]m/min were found to yield the optimum results. For the desired kerf width, MRR and [Formula: see text], the optimum process parameters were also achieved expending Taguchi’s signal-to-noise ratio. Validation results affirmed that the MCDM approach, AHP–DFA is a proficient strategy to select optimal input parameters for a preferred output eminence for WEDM of nitinol.
ESO-Based Vibration Control for All-Clamped Plate Using an Electrodynamic Inertial Actuator
Authors: Zhang Luyao , Li Shengquan , Zhu Chaowei , Li Juan
Published: October 2021

This paper proposes a disturbance rejection method with extended state observer (ESO) and a tracking differentiator (TD) to realize vibration suppression of all-clamped plate structure in the presence of lumped disturbance, i.e. internal dynamic uncertainties, unknown external forces and accelerometer measurement noises. First, the structure is modeled as two degrees of freedom system based on vibration characteristics. Second, an ESO is employed to ensure the vibration suppression performance by estimating the lumped disturbances and compensating these disturbances via real-time feedforward mechanism. Meanwhile, a TD is introduced to eliminate the influence of the measurement noises. Moreover, the stability of the closed-loop system is discussed in detail. Finally, the proposed controller is verified on the hardware-in-loop plat-form based on NI PCIe-6343 data acquisition card. Theoretical analysis and experimental results show that the proposed method possesses good vibration suppression performance.
Signal-to-Noise Ratio Enhancement by Accumulation of Signal and Noise along the Spectrum
Authors: Lebedev Igor , Dmitriyeva Elena , Bondar Ekaterina , Ibraimova Sayora , Fedosimova Anastasiya , Temiraliev Abzal
Published: October 2021

This work presents a method for background removal and signal-to-noise ratio enhancement by an accumulation of signal and noise along analyzed spectrum. In this case, the signals are accumulated, and noise, due to its chaotic nature, is suppressed. The method is applied to analyze spectra obtained on DRON-6 diffractometer for study of the crystal structure of thin tin dioxide films produced by sol–gel technology and deposited on a glass substrate. The standard analysis of the crystallographic planes of the samples under study is practically impossible due to the high noise level and the negative influence of the background from the glass substrate. The proposed method transformed the initial spectrum, which cannot be analyzed, into an informative spectrum: the background signal from the substrate is correctly subtracted and the noise decreases by 10 times. To check for possible signal distortion due to accumulation signal along the spectrum, an analysis of simulated spectra was carried out. The onset of the transition of an amorphous state to a crystalline structure of SnO2 is investigated. The crystalline structure of SnO2 thin films depending on the annealing temperature is studied.
Model structures, recollements and duality pairs
Authors: Chen Wenjing , Liu Zhongkui
Published: October 2021

In this paper, we construct some model structures corresponding Gorenstein [Formula: see text]-modules and relative Gorenstein flat modules associated to duality pairs, Frobenius pairs and cotorsion pairs. By investigating homological properties of Gorenstein [Formula: see text]-modules and some known complete hereditary cotorsion pairs, we describe several types of complexes and obtain some characterizations of Iwanaga–Gorenstein rings. Based on some facts given in this paper, we find new duality pairs and show that [Formula: see text] is covering as well as enveloping and [Formula: see text] is preenveloping under certain conditions, where [Formula: see text] denotes the class of Gorenstein [Formula: see text]-injective modules and [Formula: see text] denotes the class of Gorenstein [Formula: see text]-flat modules. We give some recollements via projective cotorsion pair [Formula: see text] cogenerated by a set, where [Formula: see text] denotes the class of Gorenstein [Formula: see text]-projective modules. Also, many recollements are immediately displayed through setting specific complete duality pairs.
A note on the boundedness of solutions for fractional relativistic Schrödinger equations
Authors: Ambrosio Vincenzo
Published: October 2021

In this paper, we obtain the boundedness of solutions for a class of fractional elliptic equations driven by the relativistic Schrödinger operator [Formula: see text], with [Formula: see text]. The proof relies on a distributional Kato’s inequality for [Formula: see text] and on some properties of the Bessel kernel.
Structure of super strongly perfect graphs
Authors: Soorya T. E. , Mathew Sunil
Published: October 2021

Super strongly perfect graphs and their association with certain other classes of graphs are discussed in this paper. It is observed that every split graph is super strongly perfect. An existing result on super strongly perfect graphs is disproved providing a counter example. It is also established that if a graph G contains a cycle of odd length, then its line graph L(G) is not always super strongly perfect. Complements of cycles of length six or above are proved to be non-super strongly perfect. If a graph is strongly perfect, then it is shown that they are super strongly perfect and hence all [Formula: see text]-free graphs are super strongly perfect.
Slopes: soil erosion
Authors: Boardman John , Poesen Jean , Evans Martin
Published: October 2021

Significant developments in soil erosion research for the period 1950–2000 are reviewed. The main emphasis is on work in western Europe and North America. We highlight work on process studies in splash, rill and gully erosion. Important developments also occurred in monitoring, measuring and modelling erosion, as well as in recording and understanding rates of erosion. We concentrate on cultivated and bare soils, and have included badlands and peatland erosion in our review.
Making weak memory models fair
Authors: Lahav Ori , Namakonov Egor , Oberhauser Jonas , Podkopaev Anton , Vafeiadis Viktor
Published: October 2021

Liveness properties, such as termination, of even the simplest shared-memory concurrent programs under sequential consistency typically require some fairness assumptions about the scheduler. Under weak memory models, we observe that the standard notions of thread fairness are insufficient, and an additional fairness property, which we call memory fairness, is needed. In this paper, we propose a uniform definition for memory fairness that can be integrated into any declarative memory model enforcing acyclicity of the union of the program order and the reads-from relation. For the well-known models, SC, x86-TSO, RA, and StrongCOH, that have equivalent operational and declarative presentations, we show that our declarative memory fairness condition is equivalent to an intuitive model-specific operational notion of memory fairness, which requires the memory system to fairly execute its internal propagation steps. Our fairness condition preserves the correctness of local transformations and the compilation scheme from RC11 to x86-TSO, and also enables the first formal proofs of termination of mutual exclusion lock implementations under declarative weak memory models.
Compiling with continuations, correctly
Authors: Paraskevopoulou Zoe , Grover Anvay
Published: October 2021

In this paper we present a novel simulation relation for proving correctness of program transformations that combines syntactic simulations and logical relations. In particular, we establish a new kind of simulation diagram that uses a small-step or big-step semantics in the source language and an untyped, step-indexed logical relation in the target language. Our technique provides a practical solution for proving semantics preservation for transformations that do not preserve reductions in the source language. This is common when transformations generate new binder names, and hence α-conversion must be explicitly accounted for, or when transformations introduce administrative redexes. Our technique does not require reductions in the source language to correspond directly to reductions in the target language. Instead, we enforce a weaker notion of semantic preorder, which suffices to show that semantics are preserved for both whole-program and separate compilation. Because our logical relation is transitive, we can transition between intermediate program states in a small-step fashion and hence the shape of the proof resembles that of a simple small-step simulation.

We use this technique to revisit the semantic correctness of a continuation-passing style (CPS) transformation and we demonstrate how it allows us to overcome well-known complications of this proof related to α-conversion and administrative reductions. In addition, by using a logical relation that is indexed by invariants that relate the resource consumption of two programs, we are able show that the transformation preserves diverging behaviors and that our CPS transformation asymptotically preserves the running time of the source program. Our results are formalized in the Coq proof assistant. Our continuation-passing style transformation is part of the CertiCoq compiler for Gallina, the specification language of Coq.
Program analysis via efficient symbolic abstraction
Authors: Yao Peisen , Shi Qingkai , Huang Heqing , Zhang Charles
Published: October 2021

This paper concerns the scalability challenges of symbolic abstraction: given a formula ϕ in a logic
L
and an abstract domain
A
, find a most precise element in the abstract domain that over-approximates the meaning of ϕ. Symbolic abstraction is an important point in the space of abstract interpretation, as it allows for automatically synthesizing the best abstract transformers. However, current techniques for symbolic abstraction can have difficulty delivering on its practical strengths, due to performance issues.

In this work, we introduce two algorithms for the symbolic abstraction of quantifier-free bit-vector formulas, which apply to the bit-vector interval domain and a certain kind of polyhedral domain, respectively. We implement and evaluate the proposed techniques on two machine code analysis clients, namely static memory corruption analysis and constrained random fuzzing. Using a suite of 57,933 queries from the clients, we compare our approach against a diverse group of state-of-the-art algorithms. The experiments show that our algorithms achieve a substantial speedup over existing techniques and illustrate significant precision advantages for the clients. Our work presents strong evidence that symbolic abstraction of numeric domains can be efficient and practical for large and realistic programs.
The semantics of shared memory in Intel CPU/FPGA systems
Authors: Iorga Dan , Donaldson Alastair F. , Sorensen Tyler , Wickerson John
Published: October 2021

Heterogeneous CPU/FPGA devices, in which a CPU and an FPGA can execute together while sharing memory, are becoming popular in several computing sectors. In this paper, we study the shared-memory semantics of these devices, with a view to providing a firm foundation for reasoning about the programs that run on them. Our focus is on Intel platforms that combine an Intel FPGA with a multicore Xeon CPU. We describe the weak-memory behaviours that are allowed (and observable) on these devices when CPU threads and an FPGA thread access common memory locations in a fine-grained manner through multiple channels. Some of these behaviours are familiar from well-studied CPU and GPU concurrency; others are weaker still. We encode these behaviours in two formal memory models: one operational, one axiomatic. We develop executable implementations of both models, using the CBMC bounded model-checking tool for our operational model and the Alloy modelling language for our axiomatic model. Using these, we cross-check our models against each other via a translator that converts Alloy-generated executions into queries for the CBMC model. We also validate our models against actual hardware by translating 583 Alloy-generated executions into litmus tests that we run on CPU/FPGA devices; when doing this, we avoid the prohibitive cost of synthesising a hardware design per litmus test by creating our own 'litmus-test processor' in hardware. We expect that our models will be useful for low-level programmers, compiler writers, and designers of analysis tools. Indeed, as a demonstration of the utility of our work, we use our operational model to reason about a producer/consumer buffer implemented across the CPU and the FPGA. When the buffer uses insufficient synchronisation -- a situation that our model is able to detect -- we observe that its performance improves at the cost of occasional data corruption.
Translating C to safer Rust
Authors: Emre Mehmet , Schroeder Ryan , Dewey Kyle , Hardekopf Ben
Published: October 2021

Rust is a relatively new programming language that targets efficient and safe systems-level applications. It includes a sophisticated type system that allows for provable memory- and thread-safety, and is explicitly designed to take the place of unsafe languages such as C and C++ in the coding ecosystem. There is a large existing C and C++ codebase (many of which have been affected by bugs and security vulnerabilities due to unsafety) that would benefit from being rewritten in Rust to remove an entire class of potential bugs. However, porting these applications to Rust manually is a daunting task.

In this paper we investigate the problem of automatically translating C programs into safer Rust programs--that is, Rust programs that improve on the safety guarantees of the original C programs. We conduct an in-depth study into the underlying causes of unsafety in translated programs and the relative impact of fixing each cause. We also describe a novel technique for automatically removing a particular cause of unsafety and evaluate its effectiveness and impact. This paper presents the first empirical study of unsafety in translated Rust programs (as opposed to programs originally written in Rust) and also the first technique for automatically removing causes of unsafety in translated Rust programs.
One down, 699 to go: or, synthesising compositional desugarings
Authors: Bartha Sándor , Cheney James , Belle Vaishak
Published: October 2021

Programming or scripting languages used in real-world systems are seldom designed with a formal semantics in mind from the outset. Therefore, developing well-founded analysis tools for these systems requires reverse-engineering a formal semantics as a first step. This can take months or years of effort.

Can we (at least partially) automate this process? Though desirable, automatically reverse-engineering semantics rules from an implementation is very challenging, as found by Krishnamurthi, Lerner and Elberty. In this paper, we highlight that scaling methods with the size of the language is very difficult due to state space explosion, so we propose to learn semantics incrementally. We give a formalisation of Krishnamurthi et al.'s desugaring learning framework in order to clarify the assumptions necessary for an incremental learning algorithm to be feasible.

We show that this reformulation allows us to extend the search space and express rules that Krishnamurthi et al. described as challenging, while still retaining feasibility. We evaluate enumerative synthesis as a baseline algorithm, and demonstrate that, with our reformulation of the problem, it is possible to learn correct desugaring rules for the example source and core languages proposed by Krishnamurthi et al., in most cases identical to the intended rules. In addition, with user guidance, our system was able to synthesize rules for desugaring list comprehensions and try/catch/finally constructs.
Transitioning from structural to nominal code with efficient gradual typing
Authors: Muehlboeck Fabian , Tate Ross
Published: October 2021

Gradual typing is a principled means for mixing typed and untyped code. But typed and untyped code often exhibit different programming patterns. There is already substantial research investigating gradually giving types to code exhibiting typical untyped patterns, and some research investigating gradually removing types from code exhibiting typical typed patterns. This paper investigates how to extend these established gradual-typing concepts to give formal guarantees not only about how to change types as code evolves but also about how to change such programming patterns as well.

In particular, we explore mixing untyped "structural" code with typed "nominal" code in an object-oriented language. But whereas previous work only allowed "nominal" objects to be treated as "structural" objects, we also allow "structural" objects to dynamically acquire certain nominal types, namely interfaces. We present a calculus that supports such "cross-paradigm" code migration and interoperation in a manner satisfying both the static and dynamic gradual guarantees, and demonstrate that the calculus can be implemented efficiently.
Coarsening optimization for differentiable programming
Authors: Shen Xipeng , Zhang Guoqiang , Dea Irene , Andow Samantha , Arroyo-Fang Emilio , Gafter Neal , George Johann , Grueter Melissa , Meijer Erik , Shivers Olin Grigsby , Stumpos Steffi , Tempest Alanna , Warden Christy , Yang Shannon
Published: October 2021

This paper presents a novel optimization for differentiable programming named coarsening optimization. It offers a systematic way to synergize symbolic differentiation and algorithmic differentiation (AD). Through it, the granularity of the computations differentiated by each step in AD can become much larger than a single operation, and hence lead to much reduced runtime computations and data allocations in AD. To circumvent the difficulties that control flow creates to symbolic differentiation in coarsening, this work introduces phi-calculus, a novel method to allow symbolic reasoning and differentiation of computations that involve branches and loops. It further avoids "expression swell" in symbolic differentiation and balance reuse and coarsening through the design of reuse-centric segment of interest identification. Experiments on a collection of real-world applications show that coarsening optimization is effective in speeding up AD, producing several times to two orders of magnitude speedups.
Dynaplex: analyzing program complexity using dynamically inferred recurrence relations
Authors: Ishimwe Didier , Nguyen KimHao , Nguyen ThanhVu
Published: October 2021

Being able to detect program runtime complexity is useful in many tasks (e.g., checking expected performance and identifying potential security vulnerabilities). In this work, we introduce a new dynamic approach for inferring the asymptotic complexity bounds of recursive programs. From program execution traces, we learn
recurrence relations
and solve them using pattern matching to obtain closed-form solutions representing the complexity bounds of the program. This approach allows us to efficiently infer simple recurrence relations that represent nontrivial, potentially nonlinear polynomial and non-polynomial, complexity bounds.

We present Dynaplex, a tool that implements these ideas to automatically generate recurrence relations from execution traces. Our preliminary results on popular and challenging recursive programs show that Dynaplex can learn precise relations capturing worst-case complexity bounds (e.g.,
O
(
n
log
n
) for mergesort,
O
(2

n

) for Tower of Hanoi and
O
(
n
1.58
) for Karatsuba’s multiplication algorithm).
Scalability and precision by combining expressive type systems and deductive verification
Authors: Lanzinger Florian , Weigl Alexander , Ulbrich Mattias , Dietl Werner
Published: October 2021

Type systems and modern type checkers can be used very successfully to obtain formal correctness guarantees with little specification overhead. However, type systems in practical scenarios have to trade precision for decidability and scalability. Tools for deductive verification, on the other hand, can prove general properties in more cases than a typical type checker can, but they do not scale well. We present a method to complement the scalability of expressive type systems with the precision of deductive program verification approaches. This is achieved by translating the type uses whose correctness the type checker cannot prove into assertions in a specification language, which can be dealt with by a deductive verification tool. Type uses whose correctness the type checker can prove are instead turned into assumptions to aid the verification tool in finding a proof.Our novel approach is introduced both conceptually for a simple imperative language, and practically by a concrete implementation for the Java programming language. The usefulness and power of our approach has been evaluated by discharging known false positives from a real-world program and by a small case study.