Concurrent counting is harder than queuing

We compare the complexities of two fundamental distributed coordination problems, distributed counting and distributed queuing, in a concurrent setting. In both distributed counting and queuing, processors in a distributed system issue operations which are organized into a total order. In counting, each participating processor receives the rank of its operation in the total order, where as in queuing, a processor receives the identity of its predecessor in the total order. Many coordination applications can be solved using either distributed counting or queuing, and it is useful to know which of counting or queuing is the easier problem. Our results show that concurrent counting is harder than concurrent queuing on a variety of processor interconnection topologies, including high and low diameter graphs. For all these topologies, we show that the concurrent delay complexity of a particular solution to queuing, the arrow protocol, is asymptotically smaller than a lower bound on the complexity of any solution to counting

Quantum noise in optical interferometers

We study the photon counting noise in optical interferometers used for gravitational wave detection. In order to reduce quantum noise a squeezed vacuum is injected into the usually unused input port. It is investigated under which conditions the gravitational wave signal may be amplified without increasing counting noise concurrently. Such a possibility was suggested as a consequence of the entanglement of the two output ports of a beam splitter. We find that amplification without concurrent increase of noise is not possible for reasonable squeezing parameters. Photon distributions for various beam splitter angles and squeezing parameters are calculated.Comment: 15 pages, 7 figure

Design and Simulation of a BioMEMS Leukocyte Counter with Concurrent Processing

Cell counting (such as white blood cells, red blood cells) is a popular technique being used in blood testing for disease diagnosis. It can give important indication about the health condition of a patient, and give hints for doctors to effectively diagnose disease. In this poster, a BioMEMS (Bio-Microelectromechanical Systems) cell counter with concurrent processing is proposed. It has presorting stage to separate out red blood cells, white blood cells and/or other cells of interest from the microfluidic flow of blood sample. The cells are then passed to branching stage to divide it into multiple braches. Each branch allows cells to pass through the microchannel in series. The cell counting is achieved by electrical impedance sensing. By introducing concurrent counting based on branching, it leads to faster throughput and improved efficiency. The proposed BioMEMS cell counter is designed and simulated in COMSOL. Simulation results verified the correct counting function of the cell counter device

Reduction of quantum noise in optical interferometers using squeezed light

We study the photon counting noise in optical interferometers used for gravitational wave detection. In order to reduce quantum noise a squeezed vacuum state is injected into the usually unused input port. Here, we specifically investigate the so called `dark port case', when the beam splitter is oriented close to 90{\deg} to the incoming laser beam, such that nearly all photons go to one output port of the interferometer, and only a small fraction of photons is seen in the other port (`dark port'). For this case it had been suggested that signal amplification is possible without concurrent noise amplification [R.Barak and Y.Ben-Aryeh, J.Opt.Soc.Am.B25(361)2008]. We show that by injection of a squeezed vacuum state into the second input port, counting noise is reduced for large values of the squeezing factor, however the signal is not amplified. Signal strength only depends on the intensity of the laser beam.Comment: 8 pages, 1 figur

Static Safety for an Actor Dedicated Process Calculus by Abstract Interpretation

The actor model eases the definition of concurrent programs with non uniform behaviors. Static analysis of such a model was previously done in a data-flow oriented way, with type systems. This approach was based on constraint set resolution and was not able to deal with precise properties for communications of behaviors. We present here a new approach, control-flow oriented, based on the abstract interpretation framework, able to deal with communication of behaviors. Within our new analyses, we are able to verify most of the previous properties we observed as well as new ones, principally based on occurrence counting

Hoare-style Specifications as Correctness Conditions for Non-linearizable Concurrent Objects

Designing scalable concurrent objects, which can be efficiently used on multicore processors, often requires one to abandon standard specification techniques, such as linearizability, in favor of more relaxed consistency requirements. However, the variety of alternative correctness conditions makes it difficult to choose which one to employ in a particular case, and to compose them when using objects whose behaviors are specified via different criteria. The lack of syntactic verification methods for most of these criteria poses challenges in their systematic adoption and application. In this paper, we argue for using Hoare-style program logics as an alternative and uniform approach for specification and compositional formal verification of safety properties for concurrent objects and their client programs. Through a series of case studies, we demonstrate how an existing program logic for concurrency can be employed off-the-shelf to capture important state and history invariants, allowing one to explicitly quantify over interference of environment threads and provide intuitive and expressive Hoare-style specifications for several non-linearizable concurrent objects that were previously specified only via dedicated correctness criteria. We illustrate the adequacy of our specifications by verifying a number of concurrent client scenarios, that make use of the previously specified concurrent objects, capturing the essence of such correctness conditions as concurrency-aware linearizability, quiescent, and quantitative quiescent consistency. All examples described in this paper are verified mechanically in Coq.Comment: 18 page

Modelling Garbage Collection Algorithms --- Extend abstract

We show how abstract requirements of garbage collection can be captured using temporal logic. The temporal logic specification can then be used as a basis for process algebra specifications which can involve varying amounts of parallelism. We present two simple CCS specifications as an example, followed by a more complex specification of the cyclic reference counting algorithm. The verification of such algorithms is then briefly discussed

Solving the Mystery of Intrusive Flashbacks in Posttraumatic Stress Disorder (Comment on Brewin 2014)

"This article may not exactly replicate the final version published in the APA journal. It is not the copy of record."In the light of current controversy about the nature of intrusions in posttraumatic stress disorder (PTSD), the review by Brewin (2014) is timely and important. It will undoubtedly stimulate further research and guide researchers' quests for understanding the nature of flashbacks in PTSD. In this commentary, I briefly summarize and discuss key points made by Brewin and elaborate on some of the reasons behind the controversy. For example, the terms involuntary autobiographical memories, intrusive memories, and flashbacks are often used interchangeably. I propose a taxonomy revealing the key differences across these forms of memory. If flashbacks are characteristic of patients with PTSD only, it is essential that more research targeting this population is conducted with a variety of methods. Finally, some new avenues for research to study intrusive memories and flashbacks in PTSD, using a diary method and modified trauma film paradigm, are described.Peer reviewedSubmitted Versio