Vincent M. Stanford

Single-molecule mass spectrometry in solution using a solitary nanopore.

We introduce a two-dimensional method for mass spectrometry in solution that is based on the interaction between a nanometer-scale pore and analytes. As an example, poly(ethylene glycol) molecules that enter a single α-hemolysin pore cause distinct mass-dependent conductance states with characteristic mean residence times. The conductance-based mass spectrum clearly resolves the repeat unit of ethylene glycol, and the mean residence time increases monotonically with the poly(ethylene glycol) mass. This technique could prove useful for the real-time characterization of molecules in solution.

Nanoscopic Porous Sensors

There are thousands of different nanometer-scale pores in biology, many of which act as sensors for specific chemical agents. Recent work suggests that protein and solid-state nanopores have many potential uses in a wide variety of analytical applications. In this review we survey this field of research and discuss the prospects for advances that could be made in the near future.

The NIST Smart Space and Meeting Room projects: signals, acquisition annotation, and metrics

Pervasive computing devices, sensors, and networks, provide infrastructure for context aware smart meeting rooms that sense ongoing human activities and respond to them. This requires advances in areas including networking, distributed computing, sensor data acquisition, signal processing, speech recognition, human identification, and natural language processing. Open interoperability and metrology standards for the sensor and recognition technologies can aid R&D programs in making these advances. The NIST (National Institute of Standards and Technology) Smart Space and Meeting Room projects are developing tools for data formats, transport, distributed processing, and metadata. We are using them to create annotated multi modal research corpora and measurement algorithms for smart meeting rooms, which we are making available to the research and development community.

An automated acoustic systemto monitor and classify birds

This paper presents a novel bird monitoring and recognition system in noisy environments. The project objective is to avoid bird strikes to aircraft. First, a cost-effective microphone dish concept (microphone array with many concentric rings) is presented that can provide directional and accurate acquisition of bird sounds and can simultaneously pick up bird sounds from different directions. Second, direction-of-arrival (DOA) and beamforming algorithms have been developed for the circular array. Third, an efficient recognition algorithm is proposed which uses Gaussian mixture models (GMMs). The overall system is suitable for monitoring and recognition for a large number of birds. Fourth, a hardware prototype has been built and initial experiments demonstrated that the array can acquire and classify birds accurately.

Bird classification algorithms: theory and experimental results

To minimize the number of birdstrikes, a common method is to use microphone arrays to monitor and identify dangerous birds near the airport or some critical locations in the airspace. However, it was recognized that the range of existing ground-based acoustic monitoring devices is only limited to a few hundred meters. Moreover, the bird classification performance in low signal-to-noise environments such as airports is not very satisfactory. This paper summarizes the development of a high performance bird classification system using a hidden Markov model (HMM) and Gaussian mixture model (GMM). Experimental results verified the classification performance.

Guest Editors' Introduction: Pervasive Computing in Healthcare

Pervasive computing has great potential to improve healthcare, from enriching data collection and distribution to virtually bringing experts to an emergency site. This special issue samples this developing area through five theme articles that go beyond current applications to find a wider range of applicability. This article is part of a special issue on Healthcare.

Synchronizing multimodal data streams acquired using commodity hardware

We have developed tools and techniques that allow video frame level synchronization of multiple free-running commodity video cameras,microphones,and computer nodes using non-realtime operating systems.The techniques rely on physical audiovisual synchronization pulses,statistical procedures to correlate and interpolate the multiple timestamp streams,and software tools for review to produce smoothed and drift-corrected timestamp streams in our multimodal corpora. In this article we present those techniques and tools. Our project is open source and we are seeking collaborative developers for future work.

Middleware and Metrology for the Pervasive Future

Looks at the data and metrology tools developed by The National Institute of Standards and Technology for the research community, including common middleware for distributed sensor data acquisition and processing.

Physics of DNA Threading Through a Nanometer Pore and Applications to Simultaneous Multianalyte Sensing

Polymer transport is central to many biological processes, including protein translocation, bacterial gene transduction and some modes of viral infection. To better understand the mechanisms of macromolecular transport, we are studying the ability of polymers to partition into and thread through single protein ion channels. It was recently shown in our laboratory that individual molecules of single-stranded DNA and RNA can be detected and characterized as they are driven electrophoretically through a single channel formed by Staphylococcus aureus α-hemolysin. We demonstrate that polynucleotides partition more readily into one entrance of this channel than the other and that the rate at which the polymer enters the pore increases exponentially with the magnitude of the applied electrostatic potential. A simple model provides an estimate for both the height of the energy barrier that limits polynucleotide entry into the channel and the number of charges on polyanionic ssDNA that initiate voltage-driven transport through the pore. We show that polynucleotides can be used to probe the geometric properties of an ion channel, and that the interaction between the polynucleotides and a nanopore can be used to estimate the concentration of analytes in solution. A statistical analysis of the current blockades provides information about the structures of both the polymer and the nanopore.

Synchronization of data streams in distributed realtime multimodal signal processing environments using commodity hardware

We describe an API built on top of the NIST Data Flow System II, a sensor-net middleware, which allows to synchronize high volume data streams in real-time, using commodity hardware in distributed computation environments. Experiences with synchronization issues arising from working with multiple data streams in applications such as real-time multi-sensor data fusion and ad hoc video processing are addressed.