14,703 research outputs found
Distributed classifier based on genetically engineered bacterial cell cultures
We describe a conceptual design of a distributed classifier formed by a
population of genetically engineered microbial cells. The central idea is to
create a complex classifier from a population of weak or simple classifiers. We
create a master population of cells with randomized synthetic biosensor
circuits that have a broad range of sensitivities towards chemical signals of
interest that form the input vectors subject to classification. The randomized
sensitivities are achieved by constructing a library of synthetic gene circuits
with randomized control sequences (e.g. ribosome-binding sites) in the front
element. The training procedure consists in re-shaping of the master population
in such a way that it collectively responds to the "positive" patterns of input
signals by producing above-threshold output (e.g. fluorescent signal), and
below-threshold output in case of the "negative" patterns. The population
re-shaping is achieved by presenting sequential examples and pruning the
population using either graded selection/counterselection or by
fluorescence-activated cell sorting (FACS). We demonstrate the feasibility of
experimental implementation of such system computationally using a realistic
model of the synthetic sensing gene circuits.Comment: 31 pages, 9 figure
Practical Hidden Voice Attacks against Speech and Speaker Recognition Systems
Voice Processing Systems (VPSes), now widely deployed, have been made
significantly more accurate through the application of recent advances in
machine learning. However, adversarial machine learning has similarly advanced
and has been used to demonstrate that VPSes are vulnerable to the injection of
hidden commands - audio obscured by noise that is correctly recognized by a VPS
but not by human beings. Such attacks, though, are often highly dependent on
white-box knowledge of a specific machine learning model and limited to
specific microphones and speakers, making their use across different acoustic
hardware platforms (and thus their practicality) limited. In this paper, we
break these dependencies and make hidden command attacks more practical through
model-agnostic (blackbox) attacks, which exploit knowledge of the signal
processing algorithms commonly used by VPSes to generate the data fed into
machine learning systems. Specifically, we exploit the fact that multiple
source audio samples have similar feature vectors when transformed by acoustic
feature extraction algorithms (e.g., FFTs). We develop four classes of
perturbations that create unintelligible audio and test them against 12 machine
learning models, including 7 proprietary models (e.g., Google Speech API, Bing
Speech API, IBM Speech API, Azure Speaker API, etc), and demonstrate successful
attacks against all targets. Moreover, we successfully use our maliciously
generated audio samples in multiple hardware configurations, demonstrating
effectiveness across both models and real systems. In so doing, we demonstrate
that domain-specific knowledge of audio signal processing represents a
practical means of generating successful hidden voice command attacks
Differences in hearing acuity among “normal-hearing” young adults modulate the neural basis for speech comprehension
AbstractIn this paper, we investigate how subtle differences in hearing acuity affect the neural systems supporting speech processing in young adults. Auditory sentence comprehension requires perceiving a complex acoustic signal and performing linguistic operations to extract the correct meaning. We used functional MRI to monitor human brain activity while adults aged 18–41 years listened to spoken sentences. The sentences varied in their level of syntactic processing demands, containing either a subject-relative or object-relative center-embedded clause. All participants self-reported normal hearing, confirmed by audiometric testing, with some variation within a clinically normal range. We found that participants showed activity related to sentence processing in a left-lateralized frontotemporal network. Although accuracy was generally high, participants still made some errors, which were associated with increased activity in bilateral cingulo-opercular and frontoparietal attention networks. A whole-brain regression analysis revealed that activity in a right anterior middle frontal gyrus (aMFG) component of the frontoparietal attention network was related to individual differences in hearing acuity, such that listeners with poorer hearing showed greater recruitment of this region when successfully understanding a sentence. The activity in right aMFGs for listeners with poor hearing did not differ as a function of sentence type, suggesting a general mechanism that is independent of linguistic processing demands. Our results suggest that even modest variations in hearing ability impact the systems supporting auditory speech comprehension, and that auditory sentence comprehension entails the coordination of a left perisylvian network that is sensitive to linguistic variation with an executive attention network that responds to acoustic challenge.</jats:p
Effect of coarse-graining on detrended fluctuation analysis
Several studies have investigated the scaling behavior in naturally occurring
biological and physical processes using techniques such as detrended
fluctuation analysis (DFA). Data acquisition is an inherent part of these
studies and maps the continuous process into digital data. The resulting
digital data is discretized in amplitude and time, and shall be referred to as
coarse-grained realization in the present study. Since coarse-graining precedes
scaling exponent analysis, it is important to understand its effects on scaling
exponent estimators such as DFA. In this brief communication, k-means
clustering is used to generate coarse-grained realizations of data sets with
different correlation properties, namely: anti-correlated noise, long-range
correlated noise and uncorrelated noise. It is shown that the coarse-graining
can significantly affect the scaling exponent estimates. It is also shown that
scaling exponent can be reliably estimated even at low levels of
coarse-graining and the number of the clusters required varies across the data
sets with different correlation properties.Comment: 21 Pages, 10 Figures. Physica A, 2005 (in press
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