232 research outputs found
Leveraging TLA+ Specifications to Improve the Reliability of the ZooKeeper Coordination Service
ZooKeeper is a coordination service, widely used as a backbone of various
distributed systems. Though its reliability is of critical importance, testing
is insufficient for an industrial-strength system of the size and complexity of
ZooKeeper, and deep bugs can still be found. To this end, we resort to formal
TLA+ specifications to further improve the reliability of ZooKeeper. Our
primary objective is usability and automation, rather than full verification.
We incrementally develop three levels of specifications for ZooKeeper. We first
obtain the protocol specification, which unambiguously specifies the Zab
protocol behind ZooKeeper. We then proceed to a finer grain and obtain the
system specification, which serves as the super-doc for system development. In
order to further leverage the model-level specification to improve the
reliability of the code-level implementation, we develop the test
specification, which guides the explorative testing of the ZooKeeper
implementation. The formal specifications help eliminate the ambiguities in the
protocol design and provide comprehensive system documentation. They also help
find critical deep bugs in system implementation, which are beyond the reach of
state-of-the-art testing techniques. Our specifications have been merged into
the official Apache ZooKeeper project
High-throughput dielectrophoretic cell sorting assisted by cell sliding on scalable electrode tracks made of conducting-PDMS
Dielectrophoresis (DEP) as a label-free cell separation approach in microdevices has been extensively investigated for a variety of applications. 3D microelectrodes made of conducting-PDMS inherit the merit of volumetric electrodes for generating influential DEP force throughout the entire channel depth and meanwhile, exploit low-cost fabrication process by soft lithography. However, the configuration of conducting-PDMS electrodes is limited to being embedded in sidewall of flow chamber, which leads to rather low flow rate and difficulties in extension of the flow rate. We previously reported a more effective configuration with 3D interdigitated electrodes made of silicon that assist cell sliding along solid tracks, yet such device requires expensive silicon dry etching and, moreover, the track appears to be patterned with non-straight and wavy outline, which not only hinders the flow rate but also allows cell sliding to occur only along its downstream side. Here we demonstrate low-cost silver-PDMS electrode-track featuring ideally straight outline that induces rather uniform drag to drive smooth cell sliding. Such design achieves live and dead cell separation at flow rate twice as that of silicon tracks with cell loading concentration 10 times higher. It also fully utilizes the track to enable cell sliding on both of the up- and down-stream sides. Notably, we also demonstrate that this track is expandable to be V-shape for more advanced bidirectional cell sliding, which is showcased here by tumor cells separation from lymphocytes at 1.2 mL/h. Such results greatly enhance the throughput as compared to the state-of-art conducting-PDMS based cell separator
Boosting API Recommendation with Implicit Feedback
Developers often need to use appropriate APIs to program efficiently, but it
is usually a difficult task to identify the exact one they need from a vast of
candidates. To ease the burden, a multitude of API recommendation approaches
have been proposed. However, most of the currently available API recommenders
do not support the effective integration of users' feedback into the
recommendation loop. In this paper, we propose a framework, BRAID (Boosting
RecommendAtion with Implicit FeeDback), which leverages learning-to-rank and
active learning techniques to boost recommendation performance. By exploiting
users' feedback information, we train a learning-to-rank model to re-rank the
recommendation results. In addition, we speed up the feedback learning process
with active learning. Existing query-based API recommendation approaches can be
plugged into BRAID. We select three state-of-the-art API recommendation
approaches as baselines to demonstrate the performance enhancement of BRAID
measured by Hit@k (Top-k), MAP, and MRR. Empirical experiments show that, with
acceptable overheads, the recommendation performance improves steadily and
substantially with the increasing percentage of feedback data, comparing with
the baselines.Comment: 15 pages, 4 figure
Mucosal Immunization Induces a Higher Level of Lasting Neutralizing Antibody Response in Mice by a Replication-Competent Smallpox Vaccine: Vaccinia Tiantan Strain
The possible bioterrorism threat using the variola virus, the causative agent of smallpox, has promoted us to further investigate the immunogenicity profiles of existing vaccines. Here, we study for the first time the immunogenicity profile of a replication-competent smallpox vaccine (vaccinia Tiantan, VTT strain) for inducing neutralizing antibodies (Nabs) through mucosal vaccination, which is noninvasive and has a critical implication for massive vaccination programs. Four different routes of vaccination were tested in parallel including intramuscular (i.m.), intranasal (i.n.), oral (i.o.), and subcutaneous (s.c.) inoculations in mice. We found that one time vaccination with an optimal dose of VTT was able to induce anti-VTT Nabs via each of the four routes. Higher levels of antiviral Nabs, however, were induced via the i.n. and i.o. inoculations when compared with the i.m. and s.c. routes. Moreover, the i.n. and i.o. vaccinations also induced higher sustained levels of Nabs overtime, which conferred better protections against homologous or alternating mucosal routes of viral challenges six months post vaccination. The VTT-induced immunity via all four routes, however, was partially effective against the intramuscular viral challenge. Our data have implications for understanding the potential application of mucosal smallpox vaccination and for developing VTT-based vaccines to overcome preexisting antivaccinia immunity
Mycoplasma genitalium Lipoproteins Induce Human Monocytic Cell Expression of Proinflammatory Cytokines and Apoptosis by Activating Nuclear Factor κB
This study was designed to investigate the molecular mechanisms responsible for the induction of proinflammatory cytokines gene expression and apoptosis in human monocytic cell line THP-1 stimulated by lipoproteins (LPs) prepared from Mycoplasma genitalium. Cultured cells were stimulated with M. genitalium LP to analyze the production of proinflammatory cytokines and expression of their mRNA by ELISA and RT-PCR, respectively. Cell apoptosis was also detected by Annexin V-FITC-propidium iodide (PI) staining and acridine orange (AO)-ethidium bromide (EB) staining. The DNA-binding activity of nuclear factor-κB (NF-κB) was assessed by electrophoretic mobility shift assay (EMSA). Results showed that LP stimulated THP-1 cells to produce tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 in a dose-dependent manner. The mRNA levels were also upregulated in response to LP stimulation. LPs were also found to increase the DNA-binding activity of NF-κB, a possible mechanism for the induction of cytokine mRNA expression and the cell apoptosis. These effects were abrogated by PDTC, an inhibitor of NF-κB. Our results indicate that M. genitalium-derived LP may be an important etiological factor of certain diseases due to the ability of LP to produce proinflammatory cytokines and induction of apoptosis, which is probably mediated through the activation of NF-κB
Emergence of central recirculation zone in a V-shaped premixed swirling flame
This paper presents an experimental study on the emergence of the central
recirculation zone (CRZ) in a V-shaped premixed swirling flame, using
simultaneous measurement of particle image velocimetry (PIV) and CH*
chemiluminescence. The results show that either increasing the Reynolds number
(Re) or decreasing the equivalence ratio ({\phi}) would facilitate the
emergence of CRZ, and the inner shear layer (ISL) plays an essential role in
governing the characteristics of CRZ. Further analysis demonstrates that the
CRZ emergence can be promoted by higher ISL intensity but suppressed by
enhanced viscous diffusion owing to higher flame temperature. As such, the CRZ
formation can be interpreted as the outcome of a competition between the ISL
intensity, i.e., circulation, and the vorticity consumption due to viscous
diffusion. This competition physically corresponds to a special Reynolds
number, Re_s, defined as the ratio between the ISL circulation ({\Gamma}) and
the ISL effective viscosity ({\nu}_s), with a simplified heat loss model
proposed for the temperature and viscosity estimations of the ISL. The
outputting {\Gamma}-{\nu}_s plot yields a single boundary line separating the
cases with and without CRZ, which points to a common critical Re_s of about
637, justifying the generality of the present criterion for lean-premixed
V-shaped swirling flames of various operating conditions. Unlike most previous
works which study the CRZ of a swirling flame from the point of vortex
breakdown, the present work reveals the importance of enhanced viscous
diffusion, caused by flame heating, in suppressing the CRZ emergence
Miniaturization Design for 8 × 8 Butler Matrix Based on Back-to-Back Bilayer Microstrip
A low-cost, compact 8 × 8 Butler matrix based on a novel bilayer microstrip configuration is presented and implemented for 4.3 GHz telecommunication application. A back-to-back placed bilayer microstrip structure has been proposed to avoid using crossover. To expand operational bandwidth of the Butler matrix, a three-branch line directional coupler has been employed as 3 dB/90° bridge, and a kind of improved two-order Schiffman phase shifter has been adopted as fixed phase shifter. For application of indoor wireless communication, a compact broadband 8 × 8 Butler matrix has been designed and fabricated. The measured results show that the return loss of the matrix is lower than −10 dB, the isolation is better than 17 dB, the power distribution error is less than ±2.0 dB, the phase error is less than ±15°, and the relative bandwidth is more than 23%
- …