Chi: a scalable and programmable control plane for distributed stream processing systems

Stream-processing workloads and modern shared cluster environments exhibit high variability and unpredictability. Combined with the large parameter space and the diverse set of user SLOs, this makes modern streaming systems very challenging to statically configure and tune. To address these issues, in this paper we investigate a novel control-plane design, Chi, which supports continuous monitoring and feedback, and enables dynamic re-configuration. Chi leverages the key insight of embedding control-plane messages in the data-plane channels to achieve a low-latency and flexible control plane for stream-processing systems. Chi introduces a new reactive programming model and design mechanisms to asynchronously execute control policies, thus avoiding global synchronization. We show how this allows us to easily implement a wide spectrum of control policies targeting different use cases observed in production. Large-scale experiments using production workloads from a popular cloud provider demonstrate the flexibility and efficiency of our approach

Human HELB is a processive motor protein that catalyzes RPA clearance from single-stranded DNA

Human DNA helicase B (HELB) is a poorly characterized helicase suggested to play both positive and negative regulatory roles in DNA replication and recombination. In this work, we used bulk and single-molecule approaches to characterize the biochemical activities of HELB protein with a particular focus on its interactions with Replication Protein A (RPA) and RPA–single-stranded DNA (ssDNA) filaments. HELB is a monomeric protein that binds tightly to ssDNA with a site size of ∼20 nucleotides. It couples ATP hydrolysis to translocation along ssDNA in the 5′ to 3′ direction accompanied by the formation of DNA loops. HELB also displays classical helicase activity, but this is very weak in the absence of an assisting force. HELB binds specifically to human RPA, which enhances its ATPase and ssDNA translocase activities but inhibits DNA unwinding. Direct observation of HELB on RPA nucleoprotein filaments shows that translocating HELB concomitantly clears RPA from ssDNA. This activity, which can allow other proteins access to ssDNA intermediates despite their shielding by RPA, may underpin the diverse roles of HELB in cellular DNA transactions.[Significance] Single-stranded DNA (ssDNA) is a key intermediate in many cellular DNA transactions, including DNA replication, repair, and recombination. Nascent ssDNA is rapidly bound by the Replication Protein A (RPA) complex, forming a nucleoprotein filament that both stabilizes ssDNA and mediates downstream processing events. Paradoxically, however, the very high affinity of RPA for ssDNA may block the recruitment of further factors. In this work, we show that RPA–ssDNA nucleoprotein filaments are specifically targeted by the human HELB helicase. Recruitment of HELB by RPA–ssDNA activates HELB translocation activity, leading to processive removal of upstream RPA complexes. This RPA clearance activity may underpin the diverse roles of HELB in replication and recombination.Work in the laboratory of M.S.D. was supported by an Elizabeth Blackwell Early Career Fellowship from the University of Bristol (to O.J.W.) and Wellcome Trust Investigator Grant 100401/Z/12/Z (to M.S.D.). Work in the laboratory of E.A. was supported by NIH Grants GM130746 (to E.A.) and GM133967 (to E.A.). F.M.-H. acknowledges support from the European Research Council under European Union Horizon 2020 Research and Innovation Program Grant Agreement 681299. Work in the laboratory of F.M.-H. was also supported by Spanish Ministry of Science and Innovation Grants BFU2017-83794-P (AEI/FEDER, UE; to F.M.-H.) and PID2020-112998GB-100 (AEI/10.13039/501100011033; to F.M.-H.) and Comunidad de Madrid Grants Tec4-Bio–S2018/NMT-4443 (to F.M.-H.) and NanoBioCancer–Y2018/BIO-4747 (to F.M.-H.)

Development of new injury risk curves for the knee/distal femur and the hip for use in frontal impact testing

This report describes how new injury risk curves for the knee/distal femur and the hip were developed through reanalyses of existing peak knee impact force data. New hip injury risk curves were developed using survival analysis with a lognormal distribution. This distribution was parameterized to account for the effect of stature, which was the only subject characteristic that had a statistically significant effect on the relationship between peak force applied to the hip and the risk of hip fracture. The empirically defined effects of hip flexion and abduction from a standardized seated driving posture on mean hip fracture force were also incorporated into the lognormal distribution as mean shifts. Injury risk curves for the midsize male crash test dummy were defined by applying the stature associated with this dummy and posture of 30° flexion and 15° abduction from a standard reference posture and the standard reference posture (0°flexion, 0° adduction) to the lognormal distribution. A new risk curve describing the relationship between peak force applied at the knee and the likelihood of knee/distal femur fracture was developed by applying survival analysis to an existing dataset in which there was uncensored, left censored, and right censored peak knee impact force data. This risk curve is similar to that currently used by the NHTSA to assess the risk of AIS 2+ KTH injury. Because the fracture forces in the dataset used to develop the new knee/distal femur risk curve were primarily from tests where rigid surfaces loaded the knees of elderly midsize male cadavers, the new risk curve only applies to rigid knee impacts and this segment of the occupant population. Future work should focus on developing knee/distal femur risk curves that apply to other segments of the driving population by characterizing and accounting for the effects of subject factors and impact surface rigidity on KTH fracture forces.National Highway Traffic Safety Administrationhttp://deepblue.lib.umich.edu/bitstream/2027.42/64998/1/102508.pd

Rare-earth monosulfides as durable and efficient cold cathodes

In their rocksalt structure, rare-earth monosulfides offer a more stable alternative to alkali metals to attain low or negative electron affinity when deposited on various III-V and II-VI semiconductor surfaces. In this article, we first describe the successful deposition of Lanthanum Monosulfide via pulsed laser deposition on Si and MgO substrates and alumina templates. These thin films have been characterized by X-ray diffraction, atomic force microscopy, high resolution transmission electron microscopy, ellipsometry, Raman spectroscopy, ultraviolet photoelectron spectroscopy and Kelvin probe measurements. For both LaS/Si and LaS/MgO thin films, the effective work function of the submicron thick thin films was determined to be about 1 eV from field emission measurements using the Scanning Anode Field Emission Microscopy technique. The physical reasons for these highly desirable low work function properties were explained using a patchwork field emission model of the emitting surface. In this model, nanocrystals of low work function materials having a orientation perpendicular to the surface and outcropping it are surrounded by a matrix of amorphous materials with higher work function. To date, LaS thin films have been used successfully as cold cathode emitters with measured emitted current densities as high as 50 A/cm2. Finally, we describe the successful growth of LaS thin films on InP substrates and, more recently, the production of LaS nanoballs and nanoclusters using Pulsed Laser Ablation.Comment: 61 pages, 24 figure

Conformational and Structural Relaxations of Poly(ethylene oxide) and Poly(propylene oxide) Melts: Molecular Dynamics Study of Spatial Heterogeneity, Cooperativity, and Correlated Forward-Backward Motion

Performing molecular dynamics simulations for all-atom models, we characterize the conformational and structural relaxations of poly(ethylene oxide) and poly(propylene oxide) melts. The temperature dependence of these relaxation processes deviates from an Arrhenius law for both polymers. We demonstrate that mode-coupling theory captures some aspects of the glassy slowdown, but it does not enable a complete explanation of the dynamical behavior. When the temperature is decreased, spatially heterogeneous and cooperative translational dynamics are found to become more important for the structural relaxation. Moreover, the transitions between the conformational states cease to obey Poisson statistics. In particular, we show that, at sufficiently low temperatures, correlated forward-backward motion is an important aspect of the conformational relaxation, leading to strongly nonexponential distributions for the waiting times of the dihedrals in the various conformational statesComment: 13 pages, 13 figure

Control of traction supply power quality using locomotive PWM converter controls

Wolfs, PJ ORCiD: 0000-0001-7048-1231Railway traction systems are highly susceptible to severe harmonic distortion, poor voltage regulation and line resonances. Electric locomotives, which are concentrated high power loads, move continuously along the supply line, rendering the topography of the supply system, a time-variable. Under those conditions, the resonant impedances vary as the traction vehicle moves along the track. Parallel resonances with feeder line inductance and capacitance between feeder line and earth, cause harmonic magnification. This paper will examine the use of small retrofit converters to improve the performance of multiphase PWM rectifiers as found in locomotive applications

An Active Power Filter Method to Improve the Line Current Spectrum of PWM Locomotive Rectifiers with Load Unbalance

Locomotives in heavy haul and high speed passenger operations represent several megawatts of electrical load. Single phase power collected by a pantograph is typically rectified by multiple PWM converters. The converter switching instants are phased to ensure ripple current cancellation, assuming that the converter loads are balanced. Partial failures may result in unbalanced operation with reduced cancellation. The resulting harmonics may adversely impact the signalling systems and/or result in over voltage effects due to resonance in the overhead supply system. This paper examines a 4 MW locomotive with three rectifier modules and a device switching frequency of 900 Hz. This results in a5400 Hz ripple frequency in the mains current. Ideal balanced operation of converters is compared to anunbalanced operation case. Unbalanced cases include rectifier failures, inverter failures and changes in the relative balance of power delivered to each axle of the locomotive. This paper will consider what may be the most frequently occurring case; that of loss of load in one traction motor due to wheel slip. Current ripple cancellation is partially lost in this case and lower frequency current components can be produced. An active filter is proposed as a means to retain an acceptable harmonic performance for the locomotive

Molecular Dynamics Simulations of Organic Photovoltaic Materials: Structure and Dynamics of Oligothiophene

Molecular dynamics simulations using atomistically detailed force fields are reported to investigate the behavior of prototypical conjugated polymers in the presence of a fullerene substrate. Four-membered oligothiophene (4TH) molecules are studied adjacent to a C₆₀ phase in an architecture that is typical of the present generation of organic photovoltaic devices. The simulations focus on the structure, orientation, and conformations that develop in the 4TH phase adjacent to the surface and are compared with bulk systems. Effective conjugation lengths in 4TH chains are shifted to significantly lower values as compared with the bulk. Chain backbone torsional transitions between trans and gauche states are counterintuitively accelerated next to fullerene and are found to be strongly correlated with density fluctuations in the polymer phase. The results demonstrate the role of the substrate in controlling nanoscale morphology of the active material in solar cells and reveal qualitative changes in the temperature-dependent behavior of 4TH in the bulk and in the presence of fullerene