bluuebunny/crossref_metadata_2025_split huggingface dataset:
Maneuvering for Paper: Physical and Social Experiences of Bureaucracy in Venezuelan Amazonia
Authors: Penfield Amy 
Published: November 2016

ResumenEl presente artículo explora un caso de aprendizaje de la burocracia venezolana, que los Sanema experimentan a través de su participación en los proyectos sociales de la Revolución Bolivariana de Chávez. Este análisis se enfoca en la capacidad de maniobra que genera el papeleo burocrático, y contribuye a la comprensión de las formas de movilidad y la experiencia del Estado de manera somática en la Amazonía contemporánea. Los nuevos patrones de movimiento que involucran un desplazamiento hacia y desde las ciudades, los trámites cotidianos y maniobras efectuadas en diversas esferas sociales, no solo deben entenderse en relación con el Estado y su omnipresencia burocrática, sino también como prácticas congruentes con las costumbres tradicionales de ‘viajar en busca de conocimiento’ que involucran un vínculo estrecho entre movilidad física y social. Así, los Sanema utilizan la experiencia burocrática adquirida en este ambiente político para conseguir sus propios objetivos, en lugar de aquellos del Estado.
Increasing Prevalence of US Elementary School Gardens, but Disparities Reduce Opportunities for Disadvantaged Students
Authors: Turner Lindsey , Eliason Meghan , Sandoval Anna , Chaloupka Frank J. 
Published: November 2016

ABSTRACTBACKGROUNDWe examined the prevalence of school garden programs at US public elementary schools. The study examined time trends, demographic and regional disparities, and associations with related programs such as farm‐to‐school.METHODSAnnual surveys were gathered from nationally representative samples of elementary schools between 2006‐2007 and 2013‐2014. Annual samples ranged from 553 to 748 schools.RESULTSThe prevalence of gardens increased steadily from 11.9% in 2006‐2007 to 31.2% in 2013‐2014 (p < .001). In multivariate logistic regressions the prevalence of garden programs varied significantly by school characteristics. Gardens were more prevalent in the west than in other regions. Gardens were less prevalent at schools serving higher proportions of lower‐income students, and were more prevalent at urban schools than in suburbs, towns, or rural areas. Gardens were more common at schools with farm‐to‐school programs. Gardens also were associated with offering formal classroom‐based nutrition education.CONCLUSIONSGarden programs in elementary schools have increased over time, but there is room for wider implementation, particularly at schools serving lower‐income students. Given the role of childhood in establishing food preferences and dietary consumption habits, such programs are important and can reinforce the messages imparted through nutrition education.
Experimental evidence for negative turgor pressure in small leaf cells of Robinia pseudoacacia L versus large cells of Metasequoia glyptostroboides Hu et W.C.Cheng. 1. Evidence from pressure‐volume curve analysis of dead tissue.
Authors: Yang Dongmei , Pan Shaoan , Ding Yiting , Tyree Melvin T. 
Published: November 2016

AbstractThis paper provides a mini‐review of evidence for negative turgor pressure in leaf cells starting with experimental evidence in the late 1950s and ending with biomechanical models published in 2014. In the present study, biomechanical models were used to predict how negative turgor pressure might be manifested in dead tissue, and experiments were conducted to test the predictions. The main findings were as follows: (i) Tissues killed by heating to 60 or 80 °C or by freezing in liquid nitrogen all became equally leaky to cell sap solutes and all seemed to pass freely through the cell walls. (ii) Once cell sap solutes could freely pass the cell walls, the shape of pressure‐volume curves was dramatically altered between living and dead cells. (iii) Pressure‐volume curves of dead tissue seem to measure negative turgor defined as negative when inside minus outside pressure is negative. (iv) Robinia pseudoacacia leaves with small palisade cells had more negative turgor than Metasequoia glyptostroboides with large cells. (v) The absolute difference in negative turgor between R. pseudoacacia and M. glyptostroboides approached as much as 1.0 MPa in some cases. The differences in the manifestation of negative turgor in living versus dead tissue are discussed.
Unforgiving motivations among divorced parents: Moderation of contact intention and contact frequency
Authors: KLUWER ESTHER S. 
Published: November 2016

AbstractThis research tests the prediction that unforgiving motivations (feelings of revenge and distance) toward the ex‐spouse are associated with less reported well‐being of divorced parents and their children when the intent to maintain contact with the ex‐partner is high rather than low. It is also predicted that unforgiving motivations are associated with more reported conflict with the ex‐partner and subsequently with less reported well‐being of their children when the actual contact frequency with the ex‐partner is high rather than low. Results from an Internet sample of Dutch divorced parents (N = 108) largely support these predictions. It is concluded that unforgiving motivations can have both intrapersonal and interpersonal negative effects for divorced parents, but only when contact is frequent or intended.
Experimental and Numerical Study of the Pressure Drop in Transonic Micronozzle Flows Across Multiple Flow Regimes
Authors: Gomez Herrera Juan E. , Groll Rodion 
Published: November 2016

In the present work, the behavior of a millimeter-scale cold-gas thruster operating with the noble gases neon, argon, krypton and xenon is investigated both experimentally and numerically. In the experimental setup, the cold-gas thruster operates under vacuum conditions and the pressure drop in the system is measured at several fixed mass flow rates ranging between 0.178 mg/s and 3.568 mg/s. The estimated Knudsen numbers for all the studied cases are above the continuum flow limit 0.01. At the higher mass flow rates the studied flows are in the slip-flow regime while at the lower mass flow rates, the transition regime is reached. The experimental pressure results are compared with numerical simulations based on the compressible Navier-Stokes equations with a no-slip boundary condition and with simulations based on the Direct Simulation Monte Carlo (DSMC) method. At high values of Kn, the pressure results of the Navier-Stokes based simulations show high deviations from both the DSMC and the experimental results. This is a consequence of the discrepancy between the no-slip boundary condition used for the Navier-Stokes simulations and gas rarefaction effects in the micronozzle becoming dominant at the lower mass flow rates.
Based on the comparison between the experimental results and the Navier-Stokes based simulations, a Knudsen-dependent correcting function with four gas-independent accommodation coefficients is developed. The accommodation coefficients allow the accurate estimation of the actual pressure drop along the nozzle based on usually computationally inexpensive Navier-Stokes simulations with no-slip boundary conditions. The flexibility of the proposed approach is advantageous for the study of experimental setups operating at a large range of mass flow rates, where several flow regimes might exist, provided that a rigorous numerical distinction between continuum, slip-flow and transition regime is not essential.
Investigating the Structure of the Bi-Layered Gas Diffusion Layer Using X-Ray Computed Tomography
Authors: Banerjee Rupak , Liu Hang , Hinebaugh James , Bazylak Aimy 
Published: November 2016

One of the most important objectives of the GDL in a PEM fuel cell is the transport of reactant gases from the gas flow channels to the reaction sites at the catalyst layer. Most state-of-the-art GDLs are composed of a carbon fiber paper coated with a microporous layer composed of carbon nano-particles. This bi-layered GDL structure has been proven to provide significant improvement to the performance of PEM fuel cells.
In order to improve our understanding of reactant transport through these GDL materials, it is important for us to characterize the structure of these materials. In this study, we use X-ray Computed Tomography (X-CT) to study the structure of the bi-layered GDL at the microscale. This work presents a unique segmentation routine developed in-house to identify the distinct components of the bi-layer GDL, isolating the carbon fiber, the microporous layer and the void regions as individual phases.
Two commercially available GDL samples, SGL 35BA and SGL 35BC are segmented with this novel algorithm to obtain unique porosity profiles. The MPL is identified separately in SGL 35BC along with the fibrous substrate region. It is observed that in the case of this sample, there is no region where only the MPL is present. The entire thickness of the MPL region is within the substrate region with fibers present throughout the MPL region. The substrate region is 300 μm thick while the MPL is present up to 200 μm from one side.
Investigation of Mixing in Colliding Droplets Generated in Flow-Focusing Configurations Using Laser Induced Fluorescence
Authors: Bedding David , Hidrovo Carlos 
Published: November 2016

Increasing the mixing rate of fluid droplets within modern lab-on-a-chip technology is being increasingly stressed by members of the biological and chemical communities that wish to study reaction kinetics and mechanisms. Faster mixing allows for a more complete analysis of a wider range of chemical and biological reactions, and due to this technologies ability to help better characterize these reactions, there is an increasingly large number of demands for chips that can fully mix droplets in an order of microseconds. High speed mixing like this is difficult to characterize using standard microscopy. This article looks at how to achieve high-speed droplet collisions using flow focusing geometry, and how these collisions are visualized using a novel laser-imaging system.
Microchannel droplet mixing is plagued with severe limitations due to the restricted microchannel lengths between elements within the chips, as well as strong surface tension forces involved and low Reynolds numbers that are found in all microchannel flow. These characteristics further reduce the rate of mixing, and thus the rate of diffusion, between the two colliding droplets. Previous attempts at mixing droplets in microchannels stemmed from two methods; hydrodynamic flow focusing, and chaotic advection mixing, this later approach leading to the advent of inertial-based droplet micromixer technology. Both of these techniques rely on rapidly decreasing the diffusion length scales between the two mixing droplets through the creation of striations. Generating these droplets while developing a method for quantifying high-speed diffusion mixing is the main focus of this article. For this study, liquid droplets are formed in a flow-focusing configuration using a high speed gaseous flow and collided at angled Y-junctions in the microchannel fabricated in PDMS. In order to determine the instantaneous rates of mixing within the internal droplet flow during the collision process, an experimental setup using epi-fluorescence microscopy in conjunction with high speed laser-induced fluorescence was developed. This setup is capable of tracking and recording fluorophore concentration within the droplets during the collision and coalescence process in multiple images. The droplets are distinguished using differing concentrations of fluorophore which correspond to differing levels of fluorescent intensity while the colliding droplets remain unmixed, and consistent levels of fluorescent intensity when the colliding droplets are fully mixed. These images are then processed using a statistical analysis software to determine both the diffusion length scale as well as the quasi-instantaneous rate of mixing at all times during the collision process.
Transient Effects in High Power Electroosmotic Pumps
Authors: Tawfik Mena E. , Gupta Shashwat , Stern Aaron , Diez F. J. 
Published: November 2016

On generating high electroosmotic flows in microfluidic pumps under applied DC voltage, the flow rate and the drawn current drop with time. When generating high electroosmotic flows using microfluidic pumps under applied DC voltage, the flow rate and current draw decrease with time. The electroosmotic (EO) pump efficiency decreases with time due to flow rate deterioration. In order to study the transient effect in EO pumps, the mass transport of ions in the membrane is investigated. Ions mass transport are affected by the membrane surface charge, ion diffusion, ion migration and flow convection. Many studies investigate the mass transport in ion selective membranes, micro-channels, and nano-channels without focus on the transient effects at high electric fields. In most of these studies, the Poisson-Nernst-Plank and the Naiver stokes equations are used to model the ion transport in electrokinetic devices. Without applying simplifying assumptions, these system of equations can be only solved numerically. A theoretical model, based on diffusion and ion migration, is developed to predict the current drop and experiments are conducted to verify this model. EO flow can be neglected when there is no membrane installed between the pump electrodes (electrochemical cell). The current drop is predicted under no flow conditions using the advection diffusion equation and it solved analytically using the Ogata and Banks solution. In order to predict the current drop in the EO pump under flow conditions, the Helmholtz-Smoluchowski equation is used to calculate the EO flow velocity. This equation holds under thin electrical double layer assumption and small zeta potential.
The current drop has been calculated theoretically and compared with the experimental data. The ion screening and depletion at the electrodes result in increasing the EO pump total resistance and decrease the total current. The calculated current drop time scale has been found to be in the order of 100 seconds under no flow conditions. As flow rate increases, the flow rate contributes to the mass transport of ions (convection current) and screens the ions faster, leading to a decrease in the current drop time scale. On the other hand, by increasing the fluid molar concentration, the current drop is much slower as more ions are available and need more time to be depleted. The current drop time scale decreases rapidly as higher DC voltages are applied, leading to low efficiency. The ion transport can be limited by applying a pulse voltage waveform instead of DC voltage, leading to more stable flow rate, current and hence constant EO efficiency. The pulse voltage waveform allows the ions to diffuse back from high to low concentration regions during the off-time, preventing ion depletion and current drop.
Polymorphic Regulation of Outer Membrane Lipid A Composition
Authors: Bishop Russell E. 
Published: November 2016

ABSTRACT

The importance of the polymorphic-phase behavior of lipid A structural variations in determining their endotoxic activities has been recognized previously, but any potential role for lipid A polymorphism in controlling outer membrane structure and function has been largely ignored until now. In a recent article in
mBio
[7(5):e01532-16, https://doi.org/10.1128/mBio.01532-16], Katherine E. Bonnington and Meta J. Kuehn of Duke University’s Department of Biochemistry make a compelling case for considering how the molecular shapes of the various lipid A structural subtypes found in the outer membrane contribute to the process of outer membrane vesicle (OMV) formation.
Dynamic synthesis for relaxed memory models
Authors: Liu Feng , Nedev Nayden , Prisadnikov Nedyalko , Vechev Martin , Yahav Eran 
Published: November 2016

Modern architectures implement relaxed memory models which may reorder memory operations or execute them non-atomically. Special instructions called memory fences are provided, allowing control of this behavior.
To implement a concurrent algorithm for a modern architecture, the programmer is forced to manually reason about subtle relaxed behaviors and figure out ways to control these behaviors by adding fences to the program. Not only is this process time consuming and error-prone, but it has to be repeated every time the implementation is ported to a different architecture.
In this paper, we present the first scalable framework for handling real-world concurrent algorithms running on relaxed architectures. Given a concurrent C program, a safety specification, and a description of the memory model, our framework tests the program on the memory model to expose violations of the specification, and synthesizes a set of necessary ordering constraints that prevent these violations. The ordering constraints are then realized as additional fences in the program.
We implemented our approach in a tool called DFence based on LLVM and used it to infer fences in a number of concurrent algorithms. Using DFence, we perform the first in-depth study of the interaction between fences in real-world concurrent C programs, correctness criteria such as sequential consistency and linearizability, and memory models such as TSO and PSO, yielding many interesting observations. We believe that this is the first tool that can handle programs at the scale and complexity of a lock-free memory allocator.
Multicore acceleration of priority-based schedulers for concurrency bug detection
Authors: Nagarakatte Santosh , Burckhardt Sebastian , Martin Milo M.K. , Musuvathi Madanlal 
Published: November 2016

Testing multithreaded programs is difficult as threads can interleave in a nondeterministic fashion. Untested interleavings can cause failures, but testing all interleavings is infeasible. Many interleaving exploration strategies for bug detection have been proposed, but their relative effectiveness and performance remains unclear as they often lack publicly available implementations and have not been evaluated using common benchmarks. We describe NeedlePoint, an open-source framework that allows selection and comparison of a wide range of interleaving exploration policies for bug detection proposed by prior work.
Our experience with NeedlePoint indicates that priority-based probabilistic concurrency testing (the PCT algorithm) finds bugs quickly, but it runs only one thread at a time, which destroys parallelism by serializing executions. To address this problem we propose a parallel version of the PCT algorithm~(PPCT). We show that the new algorithm outperforms the original by a factor of 5x when testing parallel programs on an eight-core machine. We formally prove that parallel PCT provides the same probabilistic coverage guarantees as PCT. Moreover, PPCT is the first algorithm that runs multiple threads while providing coverage guarantees.
Views
Authors: Dinsdale-Young Thomas , Birkedal Lars , Gardner Philippa , Parkinson Matthew , Yang Hongseok 
Published: November 2016

Compositional abstractions underly many reasoning principles for concurrent programs: the concurrent environment is abstracted in order to reason about a thread in isolation; and these abstractions are composed to reason about a program consisting of many threads. For instance, separation logic uses formulae that describe part of the state, abstracting the rest; when two threads use disjoint state, their specifications can be composed with the separating conjunction. Type systems abstract the state to the types of variables; threads may be composed when they agree on the types of shared variables.
In this paper, we present the "Concurrent Views Framework", a metatheory of concurrent reasoning principles. The theory is parameterised by an abstraction of state with a notion of composition, which we call views. The metatheory is remarkably simple, but highly applicable: the rely-guarantee method, concurrent separation logic, concurrent abstract predicates, type systems for recursive references and for unique pointers, and even an adaptation of the Owicki-Gries method can all be seen as instances of the Concurrent Views Framework. Moreover, our metatheory proves each of these systems is sound without requiring induction on the operational semantics.
Optimizing data structures in high-level programs
Authors: Rompf Tiark , Sujeeth Arvind K. , Amin Nada , Brown Kevin J. , Jovanovic Vojin , Lee HyoukJoong , Jonnalagedda Manohar , Olukotun Kunle , Odersky Martin 
Published: November 2016

High level data structures are a cornerstone of modern programming and at the same time stand in the way of compiler optimizations. In order to reason about user- or library-defined data structures compilers need to be extensible. Common mechanisms to extend compilers fall into two categories. Frontend macros, staging or partial evaluation systems can be used to programmatically remove abstraction and specialize programs before they enter the compiler. Alternatively, some compilers allow extending the internal workings by adding new transformation passes at different points in the compile chain or adding new intermediate representation (IR) types. None of these mechanisms alone is sufficient to handle the challenges posed by high level data structures. This paper shows a novel way to combine them to yield benefits that are greater than the sum of the parts.
Instead of using staging merely as a front end, we implement internal compiler passes using staging as well. These internal passes delegate back to program execution to construct the transformed IR. Staging is known to simplify program generation, and in the same way it can simplify program transformation. Defining a transformation as a staged IR interpreter is simpler than implementing a low-level IR to IR transformer. With custom IR nodes, many optimizations that are expressed as rewritings from IR nodes to staged program fragments can be combined into a single pass, mitigating phase ordering problems. Speculative rewriting can preserve optimistic assumptions around loops.
We demonstrate several powerful program optimizations using this architecture that are particularly geared towards data structures: a novel loop fusion and deforestation algorithm, array of struct to struct of array conversion, object flattening and code generation for heterogeneous parallel devices. We validate our approach using several non trivial case studies that exhibit order of magnitude speedups in experiments.
Subjective auxiliary state for coarse-grained concurrency
Authors: Ley-Wild Ruy , Nanevski Aleksandar 
Published: November 2016

From Owicki-Gries' Resource Invariants and Jones' Rely/Guarantee to modern variants based on Separation Logic, axiomatic logics for concurrency require auxiliary state to explicitly relate the effect of all threads to the global invariant on the shared resource. Unfortunately, auxiliary state gives the proof of an individual thread access to the auxiliaries of all other threads. This makes proofs sensitive to the global context, which prevents local reasoning and compositionality.
To tame this historical difficulty of auxiliary state, we propose subjective auxiliary state, whereby each thread is verified using a self view (i.e., the thread's effect on the shared resource) and an other view (i.e., the collective effect of all the other threads). Subjectivity generalizes auxiliary state from stacks and heaps to user-chosen partial commutative monoids, which can eliminate the dependence on the global thread structure.
We employ subjectivity to formulate Subjective Concurrent Separation Logic as a combination of subjective auxiliary state and Concurrent Separation Logic. The logic yields simple, compositional proofs of coarse-grained concurrent programs that use auxiliary state, and scales to support higher-order recursive procedures that can themselves fork new threads. We prove the soundness of the logic with a novel denotational semantics of action trees and a definition of safety using rely/guarantee transitions over a large subjective footprint. We have mechanized the denotational semantics, logic, metatheory, and a number of examples by a shallow embedding in Coq.